OpenFront Coastal Boat Defense: Stop and Reverse an Invasion of Your Home Coast

Direct answer: defend the beachhead, then reverse the drain

When enemy boats cross the water toward your home coast, the question is not “how do I stop every boat” but “how do I keep my own front from collapsing and then turn the enemy’s committed troops into a loss I can reverse.” A boat attack in v0.34 is a one-time drain of the attacker’s troops, not a standing army: the enemy right-clicks, picks Boat, and the game spawns Transport ships from their Port that each carry roughly 20 percent of the selected troops, up to three boats. That means at most about 60 percent of the force they chose is actually leaving their land; the rest stays behind, and the boats take real time to cross the water.

So the defense has two phases. Phase one is to protect the single beach where those troops land, not the entire coast. You pre-commit a wall of troops to the most likely beachhead, and if you can afford a Warship you put it on the enemy’s shortest water lane so its 250-damage shells sink transports before they reach the shore. Phase two is the counter. Because the attacker has committed most of their force to the boats, their home front is now thinner and their troop growth has dropped back toward a slower rate while they are at low strength; that is your window to push through the weakened front. The whole page below is how to size that decision: which lane to screen, how much of your own troop pool to hold in reserve, why the reserve matters for your own regen, and what goes wrong when you spread thin.

The single most common mistake this page exists to prevent is reacting to the boats by counter-attacking your entire border while they are still in transit. That commits every troop you have to a losing ratio at the moment you have the least headroom. The correct reflex is the opposite: hold one line, keep a reserve, let the boats land a smaller committed force, and hit them where they are thinnest. The rest of the guide is the numbers and the decision tree behind that reflex, and the way to hold it is to answer three small questions in a fixed order the moment the first transport appears, because a defense run out of order collapses into the same mistake it was meant to prevent. Those three questions are whether you can afford to screen the lane, whether you can deny the single beach, and whether you can keep a reserve so your own growth rate stays fast. Answer them in that order every time, and the counter takes care of itself.

How a boat attack actually works

The mechanics matter because they tell you exactly what the attacker is and is not doing. In the v0.34.11 code, choosing Boat runs the boat-attack path: it loads a number of troops equal to the floor of your selected troops divided by five, so each Transport carries 20 percent of what you selected. A second check then caps the number of boats at boatMaxNumber, which is 3. The spawned Transport ships themselves cost 0 Gold each, which is why a player with a Port can launch a boat push almost any time without spending a single unit of the economy they would otherwise need to build. Two facts follow from this that most defensive play depends on.

First, a boat attack is capped and partial. Even if the attacker selects their entire force, the game splits it across at most three boats at 20 percent each, so the force that physically leaves their land is at most about 60 percent of what they selected. The remaining 40 percent stays on their home front, and that leftover force is exactly what you are going to attack later. Second, the boats are slow relative to the game tick. Transport ships move across water tile by tile, and a channel of even 20 to 40 tiles gives them a multi-second transit. That transit is not a flaw to ignore; it is the window in which you do everything else. The attacker cannot recall the boats mid-crossing to rejoin their front, so the moment they commit, their force is split in two and the larger committed part is in motion with no way back.

The Port is the other half of the mechanism, and it is what makes the attack possible at all. A boat attack requires the attacker to have a built Port, because the Transport ships spawn from it. This is the same Port that produces Warships and Trade Ships, and it sits on the same cost ladder as a Factory: the first Port is 250,000 Gold, the second 500,000, and later ones climb to a 1,000,000 cap. If an enemy can boat you, that enemy has already paid for a Port, which means they have a real economy, and which means that if you do not have your own Port and Warship yet, the gold that would have gone to a defensive Warship is better spent finishing the Port that unlocks both your Warship and your own Trade Ships. That is why “do I have a Port” is the first question in the whole defense, before the question of whether you can spend 250,000 on a single Warship.

The three coastal-defense tests

Treat the defense as a chain of three tests that you can run in the live game, because each one changes what you do with the next 250,000 Gold and the next 5,000 troops. The tests are the affordability screen test, the denial line test, and the regen headroom test. You can pass any two of them and still lose if the third quietly fails, so the habit is to check all three at the moment the first boat appears, not after you have already committed your reserve.

The affordability screen test asks whether you have a Port and 250,000 Gold at the same time. If yes, the answer to the boat threat is almost always a Warship placed on the enemy’s shortest water lane, because a Warship’s shells do 250 damage and it targets transports first, so even one ship can sink boats before they reach the shore and it recovers when it reaches 75 percent of its 1,000 health by retreating and healing within 150 tiles of one of your active Ports. If you fail this test, you do not panic about the missing Warship; you switch to the denial line test and you route the 250,000 that would have gone to the ship into finishing the Port that eventually unlocks it. The denial line test asks whether you can hold a single beachhead with a numeric advantage. You pick the one beach the enemy will use, the shortest water lane from their Port to your coast, and you commit enough troops there that the arriving boat force fights at a disadvantage against a prepared line, not against a thin spread-out screen. If you cannot hold that single beach even at an advantage, you are under-resourced and the honest move is to fall back and protect your core Cities rather than try to win the coast.

The regen headroom test is the one most players miss, and it is the reason the next section on the regen window exists. Your own troop growth is fastest when your troop pool is low relative to its maximum, and slowest when it is near the maximum. If you commit every last troop to the coast before the boats arrive, you arrive at full strength and your regen is at its slowest exactly when the enemy lands and drains you. The test is therefore whether you are willing to keep a reserve so that, at the moment the boats land, your pool is below its maximum and your growth rate is meaningfully above its idle minimum. If you can hold that reserve, the boat attack does not just fail to break you; it hands you the refill that funds the counter. If you cannot, the defense is purely reactive and the best you can hope for is a slow retreat rather than a reversal.

Scenario: intercepting a 3-boat rush with one Warship

Use concrete numbers so the decision is not a vibe. Assume a mid-game FFA position: you hold a coast with 40,000 troops against a maximum of about 60,000, you have already built your first Port and your first Warship, and an enemy across a 40-tile channel holds 20,000 troops with their own Port. The enemy right-clicks and selects their full 20,000 for a boat attack. Because each boat carries 20 percent and the cap is 3 boats, three transports leave their land each loaded with about 4,000 troops, and 8,000 of the enemy’s force (40 percent) stays behind on their home front. That single fact is the seed of the whole win, because the enemy is now a 12,000-troop committed force in motion plus an 8,000-troop depleted front, and the committed part cannot come back.

Place your Warship on the shortest lane. Your Warship has 1,000 health and fires 250-damage shells, and it prioritizes Transport ships, so as the three transports enter the channel it intercepts the lane. Sink the first two transports before they land; each takes a few 250-damage shells, and after killing transports your Warship gains veterancy that increases its health and shell damage. When it reaches 75 percent of its maximum it automatically retreats and, being within 150 tiles of your active Port, it passively heals and repairs faster if docked within 5 tiles. One transport still gets through and lands 4,000 troops on your single beachhead.

Now the counter. You held the denial line: you committed about 8,000 troops to that one beach and kept 32,000 in reserve. The 4,000-troop landing meets your 8,000 at your prepared line and loses, because you fight at a 2-to-1 advantage at the one point the boats can reach. Meanwhile your 32,000 reserve has been below its maximum this whole time, so your growth rate is above the idle minimum and it is refilling during the fight. The enemy is down to about 8,000 with their own growth rate slowed by being at low strength. That is when you turn the Warship off the water and push through the weakened enemy front with your refilled pool. You did not stop every boat; you stopped the ones that mattered, denied the beach, kept the reserve, and the arithmetic of the 40-percent leftover did the rest of the reversing for you.

Scenario: denying a 2-boat rush without a Warship

The second scenario is the one that actually happens more, because most boat threats arrive before you have saved 250,000. Assume an earlier, tighter position: you hold 15,000 troops against a maximum of about 22,000, you have a Port but no Warship yet, and an adjacent enemy holds 9,000 troops across a short 15-tile channel. That enemy is smaller and closer, so they commit a quick two-boat rush: two transports at 20 percent each of 9,000, so about 1,800 troops per boat, 3,600 total leaving, with 5,400 (60 percent) staying on their home front. The channel is short, so the transit window is short too, and you have no Warship to screen it. The whole defense now rides on the denial line and the reserve, and on the fact that you are fighting the 3,600, not the 9,000.

Pick the single beach. With a 15-tile channel the enemy will use the closest water tile to your coast, and there is usually one obvious beachhead, the tile your nearest City or Port is on. Commit a wall of 6,000 troops to that beach and leave 9,000 in reserve. Do not spread across the channel; the boats choose the weakest segment, and a thin screen spread over the whole coast is exactly how you get beaten on the one beach that does not matter to you but breaks your front. When the two boats land, the 3,600 arriving troops meet your prepared 6,000 at a line you chose, at a ratio the attacker set by their own two-boat choice, and they lose the landing fight against a concentration they did not expect.

Then the counter, timed to the regen. Your 9,000 reserve has been below your 22,000 maximum through the fight, so your growth rate has been above the idle minimum and you are refilling. The enemy is now near 5,400 and their own growth is slowed because they committed 40 percent away. You do not need a Warship to finish this one: you push the 6,000 wall, reinforced by the refilled reserve, straight through the 5,400 enemy front. The point of this scenario is that the defense did not require you to win the water. It required you to pick one beach, refuse to spread, hold a reserve so your own regen stayed fast, and hit the 60-percent leftover that stayed behind. If you had a Warship you would have screened the lane, but the arithmetic is the same: deny the beach, keep the reserve, reverse through the depleted front.

When the defense fails and how to counter it

Most coastal losses are not caused by the boats; they are caused by the defender’s reaction to the boats. The failure mode is the reflex to counter-attack the entire border the moment you see the first transport, and the counter to that reflex is the one you should be able to recite without reading: hold one line, keep a reserve, and only then turn. Each failure below is a version of that reflex, and each has a specific correction that you can apply in the game.

The first failure is spreading thin across the whole coast. You see three boats and you move troops along the entire shoreline so that every beach is “defended.” The boats then pick the segment with the fewest troops and land there, because the attacker’s boats choose the shortest water lane, and a spread-out screen is thin everywhere. The correction is to commit to a single most-likely beachhead, the enemy’s shortest lane, and leave the rest of your coast nominally exposed but irrelevant, because a defense that is only as strong as its thinnest point is a defense with no strong point. The second failure is counter-attacking the whole border in transit. You commit your entire troop pool to pushing back across the entire front while the boats are still crossing, which means you arrive at full strength with no regen headroom and meet the boats at the worst possible ratio. The correction is the denial line plus the reserve: commit enough to hold the beach, keep the rest in reserve, and only counter after the boats have landed and committed.

The third failure is building the Warship on the wrong lane or too late. You finally save 250,000, but you build the Warship on your own side of the channel or after the boats have already reached the shore, so it never intercepts anything. The correction is to build the first Warship on the enemy’s shortest water lane and before the enemy can field boats, because a Warship that cannot reach the lane before the transports do is decoration. The fourth failure is letting one boat attack become a second. You survive the first rush, but you spent your reserve denying it and now you have no force left when the enemy, having refilled, launches a second boat push through the Port they already paid for. The correction is the reversal itself: after you deny the beach and the enemy is at 40 percent of their committed force, you push through their depleted front and take their Port, because a Port you do not deny is a boat attack that happens again. The single best defense against a repeat invasion is the counter that removes the Port that enables it.

Mode and map adjustments

The same three tests change shape depending on the map and the mode, because the transit window and the economy both scale with the water you have to cross. The most useful single adjustment is the channel length rule: the longer the water the enemy has to cross, the larger your regen window and the more a pure troop denial line can work without a Warship; the shorter the channel, the less transit time there is and the more the defense leans on a Warship screen. On a large map with a 40 to 80 tile strait, a two-boat rush gives you many ticks of transit to hold the beach, refill the reserve, and even build a Warship in response. On a compact map where the whole game is a few tiles of water, the boats cross before a denial line can fully form, so the affordability screen test becomes the deciding question and a single 250,000 Warship is worth more than an extra 5,000 troops on the coast.

In Team mode the adjustment is that a teammate’s Warship can screen your coast, which changes what you personally have to afford. If your team has already fielded a Warship and placed it on the shared water lane, your personal affordability screen test can relax, and you can commit more of your own pool to the denial line and the counter because the water is already covered by a friendly hull. The corollary is a coordination point: tell your team which coast to screen, because a Warship that patrols the wrong team lane denies nothing. In FFA there is no friendly hull, so you carry the full screen yourself, and the enemy is more likely to boat you while you are distracted by a third player, which means you should keep a standing reserve at your coast even when no boats are visible, because the cheapest boat attack in the game is one that arrives while you are looking the other way.

The mode also changes what “reverse” means. In FFA the reversal is usually total: you push through the depleted front, take the Port, and the enemy cannot re-investigate you without rebuilding the Port that took 250,000. In Team mode the reversal is often limited to protecting your team’s core and letting a teammate take the aggression, because the enemy Port may be a shared economic asset the team wants to keep alive. In both cases the arithmetic is identical, the 40-percent leftover and the regen window; only the political question of who takes the Port differs. Read the mode before you commit, because the numbers tell you the defense is possible and the mode tells you how far you are allowed to push the counter.

Reading the tables: cost, capacity, and the regen window

The tables below are the reference you use mid-game, and the way to read them is to treat the first two columns as questions you ask and the later columns as the answer they give you. The first table is the Warship cost ladder, which is the affordability screen test made concrete. The first Warship is 250,000 Gold, the second 500,000, the third 750,000, and every ship after that is capped at 1,000,000, following the formula min(1,000,000, (n + 1) x 250,000) where n is the number of Warships you already have. The practical reading is that the first ship is a real decision, the second is a commitment, and the third and beyond are reserved for protecting one named high-value target, so a coastal defense almost always runs one Warship, not a fleet.

Situation	Your state	First move	Key number
Port + 250k Gold	Can screen the lane	Build Warship on enemy shortest water lane	1,000 HP, 250-dmg shells
Port, no 250k Gold	Cannot screen yet	Route gold into Port/Warship, deny one beach	250k first Port ladder
No Port	Cannot boat or screen	Finish Port before defending	250k first Port
Enemy 3-boat rush	~40% of their force committed	Deny single beach, hold reserve	up to 3 boats, 20% each
Enemy 2-boat rush	~40-60% committed	Deny single beach, push depleted front	2 boats at 20% each

The second table is the boat capacity table, which is the denial line test made concrete. Each boat carries the floor of selected troops divided by 5, so 20 percent per boat, and the cap is 3 boats, so the maximum committed force is about 60 percent of what the enemy selected. The reading is that you are always fighting the committed part, and the committed part is at most a little more than half of the enemy’s total, which is why a denial line that beats the committed force is a denial line that beats the enemy.

Selected troops	Per boat (20%)	2 boats	3 boats (cap)	Stays home
9,000	1,800	3,600	5,400	5,400
20,000	4,000	8,000	12,000	8,000
40,000	8,000	16,000	24,000	16,000

The third reference is the regen window, which is the headroom test made concrete. Your troop growth each tick is (10 + troops^0.73 / 4) multiplied by (1 - troops / max), so the growth is fastest when your pool is a small fraction of your maximum and shrinks toward zero as you approach the maximum. The reading is that the reserve is not dead troops; it is the difference between a fast refill that funds your counter and an idle minimum that leaves you exposed after the drain. The boat transit time is the duration of that window, so a longer channel means a bigger window, which is the whole channel length rule from the mode section.

Reading your next move

Pull the page together into a single decision you can run in the live game the moment the first transport appears. Check the three tests in order: can you afford a Warship on the enemy’s shortest lane, can you hold a single beachhead at a numeric advantage, and can you keep a reserve so your regen stays fast. If you can pass all three, the play is screen the lane, deny the beach, hold the reserve, and reverse through the depleted front. If you fail the affordability test, route the gold into the Port that unlocks the Warship and lean on the denial line and the reserve instead, because a Port is worth more in the early game than the ship it enables. If you fail the headroom test, you are under-resourced and the honest move is to protect your core Cities and fall back rather than fight the whole coast.

The page you read next depends on which side of the water you are on and which question you now own. If you are planning the invasion yourself rather than stopping one, the transport landing guide is the attacker’s version of this exact mechanic, choosing the reachable coast, capping each wave, and building the beachhead. If you are specifically holding or contesting an island rather than your mainland coast, the island defense guide owns that narrower landing problem. If your question is whether to spend the 250,000 at all and how many hulls to field and where to place them, the warship fleet decisions guide is the spend-and-placement page that this one assumes you have already answered. And if your Warship is already in the fight and you want to manage its experience, its 75 percent retreat, and its docking heal, the warship veterancy guide is the per-ship reference. This page is the home-front page: it answers “the boats are coming to my coast, what do I do,” and it hands the other three their questions the moment those questions become yours. The last thing worth internalizing before you return to the game is that the defense is a sequence, not a single shot. You screen the lane or you do not, but either way you deny one beach, either way you hold a reserve so your regen stays fast, and either way the 40-percent leftover and the slowed enemy growth are doing the reversal for you. Get the order right and the boats are a drain you survive and exploit; get the order wrong and the same boats become the opening of a second invasion you have no troops left to stop.