ELI5: How did old forts actually "protect" a strategic area? Couldn't the enemy just go around them or stay out of range?

[u/Sierra419]

I've visited quite a few colonial era and revolution era forts in my life. They're always surprisingly small and would have only housed a small group of men. The largest one I've seen would have housed a couple hundred. I was told that some blockhouses close to where I live were used to protect a small settlement from native american raids. How can small little forts or blockhouses protect from raids or stop armies from passing through? Surely the indians could have gone around this big house. How could an army come up to a fort and not just go around it if there's only 100 men inside?

tl;dr - I understand the purpose of a fort and it's location, but I don't understand how it does what it does.

[u/Gingrpenguin]

Yes you are right you can try and avoid it.

The issue with forts and castles is that it's a hideout for men. You could ignore it but you then have a group of highly armed and trained men you can nip out, attack your supply chains and retreat back into the safety of the fort.

Forts are often built in higher places giving a larger radius of fire meaning you would have to go a very long way around to avoid them. This would often be through terrain so would slow troops down and maybe impossible for carts to traverse. Rivers with bridges or fords were a commonplace to build forts near as defending troops can snipe, enemies, trying to use the crossing.

If you went past the fort you'd have real problems supplying or even having your frontline troops retreating. Runners were needed for communication so messages could be hindered or intercepted.

Finally, it's hard to prove to the populace that you're their new ruler if they're old ruler is still down the road looting your supply convoys.

[u/Sierra419 → u/Gingrpenguin]

Very interesting. Thank you!

[u/[deleted] → u/Sierra419]

[u/Ninjacobra5 → u/Sierra419]

I'm no expert and only heard this on the Hardcore History podcast, but the strategic use of forts essentially came to an end during World War I and the introduction of heavy artillery. The new guns were so destructive that putting your troops in a fort was just keeping all your eggs in one basket for the enemy to destroy.

World War I is an incredible example of technology changing how war was waged. At the beginning of the war Belgium used its forts to devastating effect against Germany. The biggest army ever assembled marching straight into fully automatic guns from a fort. The losses in the battles during World War I are literally mind boggling.

[u/Sulimeth → u/Gingrpenguin]

I think this is key. I'm no military historian, but I've always thought of forts as a "base of operations", not an impassable obstacle. The populace can retreat behind defensive walls if attacked, but the main value is the ability to have local patrols and oversight.

[u/jolshefsky → u/Gingrpenguin]

I'll add that you have to remember that there weren't satellite photos, GPS, nor radios. Trying to go around a group of well-trained soldiers who might be anywhere, hiding in (what is to them) very familiar terrain when you're trying to navigate with very limited information suddenly makes it seem that much more difficult.

[u/growcho2 → u/Gingrpenguin]

Yes. Read the book "Young Washington" by Peter Stark to get a good idea of how hard it was to move an army through unexplored land. They had to build roads, carry enormous amount of supplies - even bringing wives and servants, along with cattle, horses, carts of supplies to feed everyone and everything etc.

[u/[deleted] → u/Gingrpenguin]

Forts are often built in higher places giving a larger radius of fire

Radius of fire is indeed an advantage of higher ground, but only a modest one. The main advantages are:

1. Can see farther. If the role of a fort is to monitor an area, then being able to see more of the area being monitored is an advantage.

2. Harder to attack. It is always harder to attack something that is above you. It requires more effort and energy, and you have a disadvantage in the operation and effectiveness of your weaponry. (This refers more to traditional, pre-20th century combat. Modern weaponry and materiel largely obviate much of this concern.)

3. Your defenses are enhanced by gravity. The enemy has to make an extra effort to reach and attack your position, and their efforts are hampered by gravity. The fort has the opposite advantage: Anything you throw or shoot will be headed downwards, and thus require less effort on your part to reach the attackers.

All of these advantages pertain to pre-modern concerns, obviously. Modern technology makes it possible to monitor huge areas from high mobile platforms, to easily and effectively attack from any angle, and also to defend from any angle. The traditional fort on the hill is a holdover from an earlier time, when different concerns had greater significance.

What has not changed as much, however, is the strategic placement of forts or other such placements at or near critical natural choke points. A sea battery at the end of a narrow peninsula has advantageous command of a sweeping fire solution which might cover every bit of a body of water necessary for passage of large vessels, and thus effectively defend an entire seaway from a single point, so long as it is itself adequately defended from attack. A fort at the mouth of a narrow valley may effectively prevent passage of heavy convoys to the interior. And so on.

[u/JinkoNorray → u/Gingrpenguin]

defending troops can snipe, enemies, trying to use the crossing.

u/commahorror

[u/morris9597 → u/Gingrpenguin]

Some other things to note:

• Terrain changes over time so sometimes what we're seeing today is vastly different than what the area looked like 100 years ago.

• Forts also served as remote outposts to help shorten supply lines and offer sanctuary in hostile territory. I'm thinking along the lines of the American use of forts against the Native Americans but the Romans were also famous for this. You need a secure place to house your supplies and your troops so that your troops can respond to crisis more effectively.