When Does a Nuke Break Your Own Alliance in OpenFront?

In OpenFront, launching a nuke against a player you are allied with automatically breaks that alliance the instant the missile leaves the silo — not when it lands. The break happens if either one of two triggers is true at the moment of launch: the weighted count of your ally’s tiles inside the blast circle passes 100, or even a single allied structure sits anywhere in the blast ring. You cannot see the count in the HUD, and you cannot un-launch once the missile is airborne, so the whole question of “can I hit them and keep the alliance” is decided by the geometry of their capital before you ever click fire. A carefully placed Atom bomb can erase a large chunk of an ally’s population while the alliance survives; a MIRV aimed at the same ally never survives — it severs the alliance unconditionally the moment it launches. The difference is not damage, it is which check the launcher runs, and that single fact changes which weapon you reach for when you want to wound a partner without paying the diplomatic cost of a betrayal.

The rule in one sentence

There are exactly two ways a nuke launch breaks the alliance it targets, and both are evaluated at the launch tile, not at the impact tile. The first is a quantity test: the game sums every tile of the target that falls inside the blast circle, weighting inner-radius tiles at 1.0 and outer-radius tiles at 0.5, and breaks the alliance if that weighted total is strictly greater than 100. A total of exactly 100 does not break; 100.5 does, because the comparison is > 100, not >= 100. The second is a presence test, and it is checked first in the code: if any structure that belongs to the target — a port, a factory, anything in their structure set — is inside the blast ring, the alliance breaks immediately, regardless of how few tiles are also caught. This ordering matters, because it means the structure rule can fire even when the weighted tile count is still well under 100. So the operative question before you fire is never “how much damage will this do?” but “does the blast ring cover more than 100 weighted tiles of their capital, or does it touch even one of their structures?” Answer yes to either and the alliance is already gone by the time the missile clears the silo. If the target is not your ally at all, neither trigger applies and the launch is a normal attack with no alliance consequence. The whole mechanic therefore reduces to a geometry problem you can solve with your eyes on the map: measure the blast radius against their capital, count the structures inside it, and decide which weapon keeps you on the safe side of the line. The deeper question this guide answers is not whether the break happens, but how often the two triggers actually trip against a real clustered capital, and which weapon you can still use safely when they do. The strict greater-than comparison is worth pausing on, because it is the one number that gives you a hair-thin margin: a launch that lands at exactly 100.0 weighted tiles keeps the alliance, and a launch at 100.5 breaks it, so the boundary is a half-tile of weighted population on either side. In practice you never need to resolve that half-tile by hand, because the structure rule almost always trips first on a real capital, but the strictness is the reason the threshold reads as 100 in the config while the break fires only past it, and it is the reason the guide treats the line as 100 plus a sliver rather than a hard 100.

Why launch is the moment, not impact

The most common mental model players bring in is that a nuke breaks an alliance when it hits, the way a betrayal debuff lands on arrival. The engine does not work that way. For a normal Atom or Hydrogen bomb, the alliance-break check runs in the launch sequence: once the missile is fired, the game immediately lists every ally whose capital falls inside the blast and breaks those alliances before the projectile has even finished its travel time. This is why the break is all-but-instantaneous in practice — a nuke takes a visible number of seconds to cross the map, but the diplomatic break lands at second zero, the same tick you click fire. The design consequence is that you cannot use travel time as a hedge. You cannot launch the missile, watch it fly, and hope the ally rotates their structures or you call off the blow; the decision is made and sealed at the click. The one exception to this is the MIRV warhead itself: the small warheads that fan out after the MIRV launcher fires skip the threshold check entirely at impact, which is the engine’s way of saying the MIRV’s diplomatic cost was already paid in full at the moment the launcher broke the alliance. This launch-time placement is also why the traitor debuff and the relation drop land together with the break, all at the instant of launch, rather than being spread out over the flight. For your planning, it means the launch moment is the only decision point that matters: every tile, every structure, every weighting that decides the outcome is read from the map state at that instant, and nothing that happens to the target during the missile’s flight can change whether the alliance survives. You also cannot trade off the break against the damage, because both the tile count and the structure positions are frozen at launch, so the moment you click is the moment the entire outcome is determined and there is no second chance to adjust. The launch-tick freeze also means the missile’s visible flight is pure theatre for the diplomatic question: you will see the dot cross the map for several seconds, and during that flight the target may move units, rotate structures, or even break the alliance themselves, but none of that retroactively changes the break that already happened at second zero. The one thing that can change the outcome after you click is the target’s own action: if they break the alliance or it lapses before your missile’s tiles would be checked at impact, the damage still lands but the “automatic break” framing no longer applies, because the break you were trying to avoid was already settled at launch. So the launch tick is the decision point, the flight is just the delay, and the only lever you have after the click is watching whether the target does something that changes the diplomatic state of the shot you just made.

The 100 weighted-tile threshold, decoded

The number 100 is the single constant in the whole mechanic, and it has been stable at exactly 100 across the v0.34 line, from v0.34.0 through the v0.34.22 tag this guide is verified against. To use it you have to understand what “weighted tiles” means, because the raw tile count is not what the engine compares. The blast of every nuke has two radii: an inner radius where the kill is total and an outer radius where the damage falls off. Tiles inside the inner radius each count as a full 1.0 toward the threshold; tiles that are inside the outer radius but outside the inner radius each count as only 0.5. The engine adds all of those up for the target’s tiles and breaks the alliance when the sum is greater than 100. The practical effect is that a nuke’s inner core is roughly twice as “expensive” toward the threshold as its outer ring, which rewards aiming the dense part of the blast at the densest part of their capital and lets you sometimes reach a high kill while staying under the line. Consider the Atom bomb, whose blast is an inner radius of 12 tiles and an outer radius of 30 tiles: the inner disc contributes the bulk of the weighted sum, and the wide outer skirt adds 0.5 per tile, so a thin outer arc over their capital can push a borderline launch over the threshold without adding meaningful damage. The Hydrogen bomb is the opposite problem: its blast is an inner 80 and an outer 100, so almost every tile it touches is at full weight, and any Hydrogen aimed at a populated ally’s capital will almost always clear 100 and break the alliance. That is the entire reason the Hydrogen is a declaration of war in diplomatic terms, while the Atom is the one weapon that can be a surgical, alliance-preserving strike. The weighted model also explains why the same Atom can be safe on one side of a capital and breaking on the other: shift the aim a few tiles toward the dense population and the inner disc catches more full-weight tiles, while shift it a few tiles toward the sparse edge and the same blast sits safely under the line. There is also a useful way to think about the budget when you cannot count tiles by hand: because the inner disc of an Atom is only 12 tiles across, it contributes at most a few dozen weighted points on its own, so the outer ring is what usually decides a borderline shot. That means the safe-aim skill is really a skill in managing the outer skirt — placing the 30-tile ring so its edge stops just short of the densest strip of the capital — rather than a skill in reading the inner core, which is small enough to almost never be the binding constraint on its own. The same asymmetry is why the Hydrogen’s 80-tile inner core is so much more likely to trip the threshold: its inner disc alone can approach the budget before the outer ring even enters the picture, which is another way of saying the Hydrogen’s geometry is built to break alliances, not to thread them.

The any-structure rule

The second trigger is the one players miss most, because it has nothing to do with how much of the target you are hitting. If the blast ring touches any single structure that belongs to the target, the alliance breaks at once, and this check runs before the weighted-tile count is even evaluated. A structure, for this rule, is a built object in the target’s structure set — the ports and factories that anchor their economy — not their population tiles. This makes the structure rule the dominant lever in most real games, because capitals cluster their ports and factories into a small dense cluster, and a nuke aimed at the capital is almost always going to catch at least one of them. The consequence for the safe-aim strategy is that “stay under 100 weighted tiles” is not enough on its own: you also have to keep the blast ring clear of every one of their structures, which usually means aiming at a stretch of their population that sits just outside the structures-and-ports cluster. In an early or mid game where the structures are still spread out, this is easier; in a late game where the ports have been pulled in tight behind the capital, the safe zone shrinks to almost nothing and the structure rule effectively converts any capital-level Atom into a break. The structure rule also explains a specific community observation that looks like a bug: players reporting that a nuke “broke the alliance even though it only wiped a corner.” In those cases the corner still contained one of the target’s ports, and the presence of that single structure was the trigger, not the tile count. When you are judging a safe aim, treat every one of the target’s structures as a hard no-go dot inside the blast ring and plan the shot around them as much as around the weighted-tile budget. The structure rule also has no recovery: because it is checked first and fires on a single object, there is no way to “shave” it down the way you can shave a tile count — the only fix is to move the whole blast ring off the structure, which is a bigger geometric adjustment than a small tile-budget tweak and usually the deciding factor in whether a safe aim exists at all. In a crowded endgame where the ports and the contested population strip are the same cluster, that adjustment is often impossible, which is why the structure rule, more than the tile threshold, is what makes the safe-aim window close as the game progresses and the capital pulls its economy in tight around the population you are trying to hit. The structure rule has no gradual edge the way the tile threshold does: a structure is either inside the ring or it is not, and one inside is enough to trigger the break, so the margin of safety you plan around is the distance from the nearest port to the ring, not a tile count you can shave down.

Quick reference

The table above is the whole decision at a glance, and the one column that separates a safe strike from a forced betrayal is the last. The Atom and the Hydrogen both run the threshold check, so both can in principle be fired without breaking the alliance, but only the Atom is small enough that a safe aim is usually reachable; the Hydrogen’s inner radius of 80 tiles makes clearing the structure rule and the 100 weighted-tile line at the same time nearly impossible against a clustered capital. The MIRV row is the hard stop: its launcher does not run the threshold check at all, so there is no safe aim, no weighted-tile budget, and no structure-avoidance trick that will keep the alliance alive. The cost column is worth reading together with the last column, because the MIRV’s escalating gold price — a base of 25 million plus 15 million for every MIRV already launched in the match — means it is the most expensive weapon you can buy and it is also the only one that guarantees the diplomatic cost you might be trying to avoid. If your goal is to wound an ally while the alliance holds, the MIRV is categorically the wrong tool no matter how affordable it feels. The speed column matters less for the alliance question than for the timing question covered in the next section, but it is worth noting that the MIRV travels at 15, faster than the Atom and Hydrogen at 10, so even though its break is unconditional and instant, its warheads arrive sooner than a normal nuke would. Read the cost column as a second filter: the 750K Atom is cheap enough that a misread of the safe aim is a recoverable error, while the 5M Hydrogen and the 25M-plus MIRV are investments you cannot afford to spend on a strike that also hands your ally a free betrayal, which is why the safe-aim discipline is most forgiving on the weapon you reach for least.

Scenario: a surgical Atom that keeps the alliance

Imagine you are allied with a large Nations player in the third minute of a standard game. You have an Atom bomb ready at 750K gold, and you want to shave a big bite out of their population to win a contested sector, but you do not want to pay the betrayal: the traitor debuff on yourself for 30 seconds, the −100 relation drop to them, and the −40 drop to your nearby neighbors, plus the loss of their defensive cover. Here is the safe-aim procedure with the numbers that make it work. First, read their capital. Their ports and factories sit in a cluster of maybe eight to twelve structures near the center of their population. The Atom’s outer radius is 30 tiles, so you need to place the blast center far enough from that structure cluster that no port or factory falls inside the 30-tile ring — if the cluster is 35 tiles from the edge of the population you want to hit, an aim 30 tiles out keeps you clear. Second, estimate the weighted tiles. The population strip you are targeting is maybe a hundred raw tiles, but the blast’s inner 12-tile disc catches only a fraction of them at full weight and the rest at 0.5, so a well-placed Atom on a sparse edge strip can land a total weighted count in the high eighties, safely under 100. Third, confirm the target is actually your ally and not already broken, because if the alliance is already severed the threshold check is moot and you have nothing to protect. If all three hold — structure cluster clear, weighted total under 100, alliance still intact — the launch wipes that strip of their population and the alliance survives. The assumption that breaks this play is a late game with the structures pulled tight: if the ports are now within 30 tiles of the population strip, the structure rule fires and the safe aim does not exist, and you should either accept the break deliberately or use a non-nuclear tool to contest the sector instead. The same procedure inverts cleanly when the structures are far from the population you want to hit: in that case the tile threshold becomes the binding constraint, you aim the inner disc at the densest strip, and you back the blast off just enough that the outer skirt no longer drapes over the port cluster, trading a little damage for a clean, alliance-preserving strike that leaves the partner able to keep covering your flank. One detail worth internalizing from this scenario is that the safe aim is a per-shot decision, not a per-alliance one: the same Atom that is safe in the third minute against a spread-out capital can be breaking in the sixth minute against the very same player once their ports have pulled in, so the checklist has to be re-run on the current map state every single time you raise the launch cursor, and you cannot bank a “safe aim” you found earlier. That is also why the community reports of a “suddenly broken alliance” that had not been broken before are usually not a bug but a geometry change: the target rebuilt or rotated their structures into the ring between two of your shots, and the second shot crossed the line that the first one did not, which is exactly the behavior the structure rule is supposed to produce.

The MIRV: the threshold does not apply

The MIRV is the one nuke that ignores the entire threshold and structure analysis above, and understanding why is the second most important fact in this guide. When the MIRV launcher fires, it does not run the weighted-tile or structure check the Atom and Hydrogen run. Instead, if the player the MIRV is targeting is one of your current allies, the launcher breaks that alliance unconditionally the instant it launches, and it also sets the mutual relation to −100. The launcher then spawns 350 individual warheads that fan out across the target region, and those warheads, when they land, skip the alliance-break check again — the engine has already collected the diplomatic toll at launch, so there is nothing left to check at impact. The design logic is simple and worth internalizing: the MIRV is so large and so destructive that the game treats firing it at an ally as an unconditional act of war, with no geometry-based safe zone to aim for. This is the exact opposite of the Atom’s design, where the game lets you stay under the line if your aim is disciplined enough. The practical consequence is a clean rule: if you are allied with the player you intend to MIRV, you will break the alliance no matter where you aim, no matter how few of their tiles you touch, and no matter how you scatter the warheads. The only way to use a MIRV against an ally without a forced break is to not be allied with them at the moment of launch — either the alliance has already expired, you have already broken it deliberately, or you were never allied. The 350-warhead count also matters for the damage side of the decision: a single MIRV is a regional weapon that can flatten entire capital clusters, which is precisely why the game refuses to let it be used as a surgical, alliance-preserving strike. If your plan requires the alliance to survive the shot, the MIRV is off the table and the Atom is the only nuclear option left. The escalating cost reinforces the same point: because each MIRV you launch makes the next one 15 million gold more expensive, a MIRV is a once-per-match statement rather than a repeatable tool, and spending that statement on an ally you wanted to keep is the most expensive way to hand them a betrayal you could have avoided with a single Atom.

When it does not break: self-nukes and the edge cases

The alliance-break mechanic only fires against allies, so a whole class of nuke usage is exempt from the threshold entirely. The most important case is nuking yourself. Your own tiles and your own structures are not counted toward the threshold, because the check only looks at the tiles of players who are currently allied with the launcher and are not the launcher. This is the engine’s way of allowing the well-known self-nuke play: if you are locked behind a wall of SAM launchers that your own nukes cannot reach, you can nuke your own position to clear the air and force your own SAMs down, and no alliance is broken because you are not allied with yourself. The same logic covers nuking a player who is not your ally at all — an enemy, a neutral, or a player whose alliance with you has already expired or been broken — because the check has no ally to break and the launch is a normal attack. There is also the trivial case where you have no alliances at all, in which case the check finds no allies in the blast and nothing can break. These exempt cases are worth stating explicitly because they explain several community reports that look like the mechanic is inconsistent. A player who self-nukes to bypass their own SAMs and sees no betrayal is not experiencing a bug; the threshold simply does not apply to self or to non-ally targets. The one nuance to watch is the boundary between “allied” and “not allied”: if the alliance is in the process of expiring, the state at the exact launch tick is what matters, and a launch that fires one tick before the alliance lapses still runs the check against a still-alive ally. So the safe-aim discipline does not relax at the very end of an alliance window; it only relaxes once the alliance is genuinely gone and the target no longer counts as an ally for the launch that fires after that moment. There is also the multi-ally case, which is where the mechanic gets genuinely interesting: the check runs against every ally whose capital falls inside the blast, so a single Atom can break one alliance while leaving another intact if only one of your two partners sits in the ring. That means the threshold is evaluated per-ally, not once for the whole blast, and a shot that breaks your main partner can be perfectly safe with respect to a secondary partner standing just outside the ring, which is a distinction worth checking whenever you are allied with more than one player near the target.

Failure modes and the pre-launch checklist

The ways this mechanic bites players are specific and predictable, so the final section turns them into a checklist you can run in the few seconds before you click fire. The first failure is the structure trap: you stay under 100 weighted tiles but the blast still catches one of the target’s ports, and the alliance breaks anyway because the structure rule runs first. The fix is to treat every one of the target’s structures as a hard no-go dot and verify the blast ring is clear of all of them, not just the tile count. The second failure is the outer-arc miscalculation: you aim the inner core safely but a thin outer skirt of the blast drapes over a large chunk of their capital at 0.5 weight each, and the accumulated 0.5s push the total over 100. The fix is to weight the outer ring in your mental sum, remembering that a wide outer arc is roughly as expensive toward the threshold as a smaller inner disc. The third failure is aiming a Hydrogen as if it were an Atom: the Hydrogen’s 80-tile inner radius makes the safe zone effectively nonexistent against a clustered capital, and firing it at an ally’s capital is a break in almost every geometry. The fix is simple — the Hydrogen is for enemies, not for allies you want to keep. The fourth failure is the MIRV assumption: players sometimes believe that scattering the MIRV warheads across the map or aiming the launcher at a sparse area will dodge the break, but the launcher breaks the alliance unconditionally at launch, so there is no scatter pattern that helps. The disciplined pre-launch checklist, in order, is: is the target actually my ally right now; is the blast ring clear of every one of their structures; is the weighted tile sum, inner at 1.0 and outer at 0.5, strictly under 100; and am I using an Atom rather than a Hydrogen or a MIRV. If any of those answers is no, the safe aim does not exist, and the correct move is either to accept the break deliberately with the traitor cost in mind, or to contest the objective with a non-nuclear tool. This checklist, run in the seconds before the click, is the whole discipline of the mechanic: it is the same decision the Nation alliance decision guide makes at the moment of a deliberate break, applied to the automatic break that a nuke launch triggers, and it sits alongside the general alliance and betrayal strategy rules for the traitor window and the relation drops that a forced break forces you to live with. For the deeper timing of when a deliberate break is worth that cost, see alliance break timing, and if your plan is to nuke through water, read water nukes first, because the conversion changes the blast geometry the checklist measures.