OSR: Coastal Defense Forts and Starcraft

Wait, what?

Let me explain. I've been reading a lot of sailing nonfiction for my pirates game. Again and again in books about Age of Sail warfare, the phrase, "silenced the coastal batteries" appears. If sailing into a port and destroying the defenses was so easy, why were the defenses present at all?
Barbara W. Tuchman has the same complaint in The First Salute.
It was one of the peculiar malfunctions of technology that shore batteries on the islands were generally of inadequate caliber and range to knock out a ship approaching with hostile intent. One is moved to wonder why, if a 10-pounder gun could be mounted on the rolling deck of a sailing vessel, the same or larger could not be mounted on land? The fact is that the blind parsimony of the defense kept the shore batteries usually too few in number to equal in firepower the heavy guns of a ship of the line. When one of these big ships engaged in an exchange with shore batteries, it was more likely to knock out the land guns than vice versa. The guns of Fort Orange, like those of other islands, can still be seen mounted in the courtyard of the fort pointing right down at the harbor. If they could not defend against a landing force, what were they for? Silent, technology has no answer.
-Tuchman, The First Salute

Technology might have no answer, but economics does.

A Very Brief Introduction To Starcraft

Starcraft (and Starcraft II) are real-time strategy video games. 1v1 competitive Starcraft is a bit like chess. There's a simple goal (destroy your opponent's production structures) but no defined way to reach that goal. There's no checkpoints, no hints, no linear progression. Units might have restrictions and abilities, like in chess.

Simple version: Your workers mine minerals. You spend minerals to build units (mobile, deals damage) and structures (immobile, produce units).  One type of structure is a turret (immobile, deals damage).

In high-level competitive play, where optimal plays are determined by microsecond timing and thousands of hours of practice, turrets are relatively rare.


Resource Trading

You have enough minerals to build either a unit or a turret. With no other information, what  do you build?

The answer is, almost always, the unit.

A turret is immobile. It will protect an area if you are attacked, but if you aren't being attacked it's just sitting there. It's wasted minerals. In a highly competitive game with razor thin margins, wasted minerals, especially in the early stages of the game, are a death sentence.

A unit is mobile. You can use it to acomplish the purpose of the game; get to your opponent and kill their structures. A turret doesn't help  you win games. It just helps you not lose.

And it doesn't even help very much. It might pick off a few units, but if your opponent shows up with a large number of units they can destroy the turret before it gets a chance to fire.

Yet turrets are still built from time to time. Why?
Team Liquid

Preventing Harassment

Most of the time, you want your units to be away from your structures, doing damage and preventing your enemy from gaining control of the map. You want to be investing your minerals in structures (to make more units) and units (to win the game). If your structures are undefended, one unit from your opponent can sneak in, kill your workers, and slow down your flow of minerals. Your opponent, meanwhile, is still gaining minerals and can build more units and structures.

You don't want to keep units back, so you put down a turret near your workers. This prevents casual harassment. One or two units will be picked off before they can deal enough damage to earn back their cost. If your opponent invests in a large number of units and sends them in, sure, the turret won't do much, but that wasn't the point of building it. You want to make it more costly for a small number of units to deal damage. If you're doing a very strange build order, turrets can also keep you alive long enough to get your units out.
Fort Denison, Sydney Harbour. Wikipedia.

Small Coastal Forts

A coastal fort, particularly the ubiquitous Martello tower, is the equivalent to a Starcraft turret.

You don't want a ten gun pirate sloop to roll in and burn your town. A coastal fort with any number of guns makes taking a harbour a significant challenge for a small crew and a small ship. But when a fleet shows up, the coastal fort is mostly useless. It's job is not to protect the harbour. It's job is to make the harbour more difficult to take; too difficult for a casual pirate or a lone ship.

You also want to invest the minimum amount of money in your forts. Most of the time they don't do anything. Given the choice between a ship - capable of blockading port, capturing enemy vessels, carrying letters, diplomats, and cargo, and winning wars - and a stationary fort, simple economics says you invest in ships. Forts were often small and, compared to the ships that took them, undergunned, but that's the point. Until the age of accurate artillery, it's far more sensible to put your cannons on a mobile platform than an immobile one.

Applying This To RPGs

In domain-level games, players want to defend "their stuff." They've got a town, a port, a village, a pile of loot and they don't want anyone else taking it.

Building a fort seems like a logical step, but given their limited resources, it might be easier to anchor a ship in the harbour and use it as a floating fort. It's not ideal - it's far easier to board, steal, or bribe a ship - but it's enormously cheaper. If things go sideways the ship can also run away and fight another day; a fort will just be turned against them.

More Quotes

The fleet having secured the landing and an excellent harbor, a squadron with two brigades was dispatched to the bay of Petite Anse to take up station there, and another squadron to Grande Anse. When Captain Hervey of the Dragon had silenced the battery, Rodney’s marines and seamen attacked and took possession of the fort. “On January 14th I followed with the whole fleet and army,” having again destroyed the enemy’s batteries on shore. After reconnoitering the coast here, he determined with General Monckton to attack Fort Royal on the 16th. And having “very successfully and with little loss silenced the batteries [which seemed to have registered on this occasion a more than ordinary record of uselessness], I landed General Monckton with the greatest part of his forces by sunset; and so the whole army was on shore a little after daylight next morning, without the loss of a man,” with all necessary supplies, and “all ships and transports anchored as much in safety as this coast will admit of.”
-Tuchman, The First Salute

The layman, looking at [Hadrian's wall's] imposing size - it was originally about twenty feet high and ten feet wide , and although no part of it today is as tall as this, it is still an awe-inspiring barrier - may be excused for thinking it was  a defensible castle wall on a gigantic scale. In fact, it was not intended to be a Maginot line. As Viscount Montgomery has pointed out, it was a deterrent rather than a defense, which could never have resisted a well-organized invasion , and indeed wild men from the north overran it and its chain of castles and platoon strongpoints on at least three occasions.
-Fraser, The Steel Bonnets

Tasteless: "There's no cannon. THERE'S NO CANNON! Where's the cannon?"
Artosis: "There is no cannon, you just said it yourself." 
-Casting GSL Season 2 Ro16 Group D, 2014


  1. A very solid analysis. It should be noted that when the number of guns were equal, the shore batteries had the advantage (much more stable firing platform) - so half a dozen cannons could easily keep invaders at bay. But this was not guaranteed - the soldiers manning the fort could be poorly trained, absent, bribed etc. And the fort was vulnerable to landing parties.

    Although I know that O'brian's series (Aubrey-Maturin) is fiction, it is very well researched, and I recommend it again :) In the first book such shore batteries featured more than once.

    1. And sometimes they worked pretty well! https://en.wikipedia.org/wiki/Torra_di_Mortella

  2. This reminds me of a more closer-to-home example: bicycle locks. A lock will not stop a determined thief (hacksaws, chain cutters and other tools make short work of them), but it will deter them by making the act so obvious and time-consuming as to not be worth it.

    The determined thief, then, is the armada, and the thief that's just out for a quick buck is the ten-cannon ship. Nothing you can do will stop the former, but by installing some cannons you can prevent the latter from nicking your bike.

    On a similar note, this extends to non-high-end locks in general. Unless you live in a vault locking your front door isn't going to stop a determined thief, just maybe make them think twice before deciding to break your window. This applies to D&D as well: a locked door doesn't actually require a key or Thief, just a Fighter with a grudge to bear against doors. In both cases, however, the lock might win on account of the would-be burglars being wary of wandering monsters (be they police, orcs, or orc police).