How to limit naval combat in a world of giant canals

Question

My world is a drier variant of Earth and the civilization there has built a massive canal network that is used for moving water from the pole to the temperate zone as the temperate zone is lacking in water.

The original builders of the canal network are gone and civilization has regressed back to ancient technology (pre steam) with multiple nations occupying the canal network. The canals are roughly 400m wide and 10m deep and are also used for commerce. The cities are located on the intersections between canals.

I’m am using this world as a setting for a large wargame campaign and I’m interested to fight a lot of land battles but I would like to minimise the navel combat aspect as it makes things too complex. How can I reasonably prevent or limit naval conflict in my world?

Answer 1

Chain boom.

https://en.wikipedia.org/wiki/Hudson_River_Chain

In the Revolutionary war some American waterways were defended with chains. The chains spanned the river, just underwater, and were intended to stop British ships traveling upstream. Some sites worked better than others. At the mooring points of the chains there were batteries, presumably to shoot at any ships that hung up in the chain and also to defend the mooring points of the chain.

Captain Thomas Machin, the Artillery Officer and engineer who had installed the chain at Fort Montgomery, was assigned to the same task at West Point. On 30 April 1778, he directed the installation of the chain across the river. Its southern end was secured to a small cove on the West Bank of the river and its northern end was anchored to Constitution Island. The West Point side was protected by Chain Battery and the Constitution Island side by Marine Battery. Both ends were anchored to log cribs filled with rocks. A system of pulleys, rollers, ropes, and mid-stream anchors were used to adjust the chain's tension to overcome the effects of river current and changing tide. Until 1783, the chain was removed each winter and reinstalled each spring to avoid destruction by ice. A log "boom" (resembling a ladder in construction) was built to span the river about 100 yards (91 m) downstream (south of the chain) to absorb the impact of any ship attempting to penetrate the barrier. The British never attempted to run the chain.

The chain depicted is not the Hudson one but a similar one from West Point. You can still go see salvaged links.

In your world, you could have chain booms to curtail canal use by enemies. It should be much easier than on a river since canals are artificial and usually have artificial controls on water flow. The article describes trouble with the chain related to ice and other natural phenomena.

Answer 2

Think Panama. The Panama Canal is made up of a series of gates which would greatly slow down ships made for combat. Controlling tight canals means that you could feasibly move some sort of Navy through them (or block other navies), but getting control of the canal sides themselves would be more important for that, meaning that ground combat was still the main method.

If anything, controlling the canals would be most important for getting supplies to a fortified position. A fort built by a canal could conceivably stay supplied indefinitely during a siege, if the canal itself were held by friendly forces. That said, keeping combat out of the canals would be possible if these supply ships were small enough to stick to one bank away from enemy fire or something along those lines.

Having NO naval combat is unrealistic if the canals are as widespread as they seem, but you could definitely make it more difficult for it to be a reasonable.

Answer 3

If the nations occupying these canal networks have cannons, there isn't going to BE any naval combat.

Not anywhere within range of land-based artillery at any rate. It's always cheaper and easier to put your cannons in a fortification than on a boat, and you can put MUCH larger cannons in a fortification more easily than you can on a boat. The advantage of warships, in a fifteenth/sixteenth century technological setting is that they can go anywhere there's water, but in your setting that advantage is reversed. The canals provide a massive advantage to defenders in any kind of military engagement. Mobility offers no advantage if you can't use it to move past your opponent without engaging him, and canals make that impossible.

The only time you might have ship-on-ship combat would be out in the middle of nowhere, in areas where neither side has fortifications or cities. Even here, the most effective tool would be the biggest, slowest, most heavily armed floating platforms you can build. Even then, you couldn't bring something like that in range of an enemy ground emplacement without assaulting it on LAND first and disabling its guns.

Your civilizations might have had extensive naval battles at a technology level equivalent to the first or second century, when weapons didn't really exist that could disable ships from 3-400 yards away. You might have had great naval engagements on par with the Battle of Salamis where the Greeks beat the Persians

The moment someone invented even a really good trebuchet though, it would spark a spectacular arms race towards massive defensive artillery, and nothing that floats could get anywhere close without their permission. That means that wars between these nations would primarily be conducted with CAVALRY, not ships, operating out in the open areas in between canals and cities, raiding smaller towns and burning crops and so forth. The only way to take a defended city would be by seiging it and cutting off it's food supply first, and you can't do that with ships in this scenario.

The main use I see for ships in this setting is as cargo vessels. You'd us them to move your troops long distances more quickly than they could march, but you'd disembark them for actual combat. Other than that you might have fast galleys being used as scouts and maybe commerce raiders, and they'd get in 2 and 3 ship squabbles sometimes, but they'd be useless for actual large scale warfare between nations.

Answer 4

Coastal batteries can be built much larger, better armored & camouflaged and would in this case get a distinct advantage in ranging. You know exactly where the canal is and at which position the ships is. The ship you are engaging has to establish a distance first. Put your artillery on a hill and you get both an additional energy advantage and cause potential problems with gun elevation for your target.

Add chains or Czech hedgehogs as temporary blockages into the mix. Those ships are more of a liability then an asset. Their main use would involve the covert transport of arms and other supplies, always hoping they won't get seized.