In the story I'm working on, there's an island kingdom that has historically been attacked by invaders from the mainland. This island kingdom's culture is akin to that of ancient Djibouti or Eritrean people, while the invaders share more similarities to the Ottomans.

My question is what would it take for these island people to successfully fend off invaders for centuries? Sure, they may know more about the climate/topography of their own home (the region is supposed to have strong winds), but what kind of fortifications would they have to build in order to survive as an independent nation? I ask because I'm not particularly familiar with medieval warfare and defenses beyond moats, catapults, and walls.

EDIT: Yes, my question is more geared towards what resources will it take to defend against a larger mainland invader. As I mentioned climate could work in their favor, such as strong winds, but some of their own ingenuity could be incorporated with this advantage... possibly bolstered by it as well. I had no plans on having these islands experience regular volcanic activity, but their use of this natural phenomena could be entertained as well.

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    $\begingroup$ What's the island's shore look like? Can invaders land anywhere, or there are only a few suitable landing areas that could be fortified and defended? $\endgroup$
    – Alexander
    Apr 29, 2019 at 18:19
  • $\begingroup$ Is there a continental shelf, or is the island a volcanic isolate? You've mentioned culture (ancient Djibouti or Eritrean - how far back, stone age?), how about tech level and available resources (nature and quantity) for the islanders? Or is that what you're asking - "What resources would it take?" , you'd need to edit the question to clarify. $\endgroup$ Apr 29, 2019 at 18:29
  • $\begingroup$ Ok I see your edit, perhaps you could consider using the sandbox to develop your question, whilst you do some research into the period you seem to want to write about: worldbuilding.meta.stackexchange.com/questions/639/… Meanwhile I'm voting to close the question as unclear what you are asking. $\endgroup$ Apr 29, 2019 at 18:37
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    $\begingroup$ How big is the island? This is crucial. It's one thing to defend Ithaca, another to defend Malta, and yet another to defend Great Britain. $\endgroup$
    – AlexP
    Apr 29, 2019 at 18:41
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    $\begingroup$ @aniben, make sure you edit your question. Never trust that people will read through the comments to find all the clarifications. Per our help center, questions must be "specific and answerable." The phrase "isn't large" doesn't mean anything. And unless your islanders have a wonderful navy, an island chain like the Hawaiians would be impossible to defend for centuries ... or unless the island is very far away from the mainland (e.g., not enough provision to transport 2,000 troops without bigger boats they don't have the tech for). $\endgroup$
    – JBH
    Apr 30, 2019 at 0:42

3 Answers 3


1. Elevated fortifications with long distance projectile weapons, overlooking the harbor.

2. Walls that everyone can hide inside.

Here is Tyre.


They held out against Alexander for a long time because of #1 and #2.

Here is Montjuic, at Barcelona.


A couple of centuries worth of obsolete cannon are up there. They definitely have a commanding view of the old harbor. Who needs walls when you can drop projectiles on people from an elevation like that?

Constantinople is the most awesome of these I know about. That city had walls all the way around, preventing attack by land and from the sea.

So too your people. They can have an elevated fortress with catapults overlooking the harbor. The walls on the interior landward side can be defended against landing parties. If invaders show up, people from the countryside can come shelter in the castle until they are repelled.


I direct you to two island with similar names and histories but which are on opposite sides of the Channel Saint Michael's Mount in Cornwall and Mont-Saint-Michel in Normandy. Both are ridiculously defensible because they have high walls down to what was, at the time of construction, the low-tide mark, its not that sea-level has changed much but the interruption the fortifications cause to long-shore currents has caused a lot of sand to pile up and compromised their original defenses. Any island far enough off shore that boats are a must have for an attempted assault can be defended almost indefinitely, with sufficient supplies, if you run a strong wall up from the waterline to a height that ship mounted scorpions can't fire over it. During the early-middle medieval period anyway, once ship based bombards start playing a role in maritime warfare walls are no longer the defense they once were, which doesn't make them useless just imperfect.

Note well that this approach breaks down rapidly as you expand the area of your kingdom.


Some suggested elements of defense would be a coastal guard that serves to warn the main city of an oncoming attack, a naval fleet with the mission of intercepting the attackers before they reach land, some form of fortification on waterways leading inland, and artillery located inside of said fortification. Historically most attacks occurred after the attackers had sailed upriver to reach a city, in this case, the fortifications and artillery would be of the most importance. If your city is directly on the coast of the island, the naval force would be a better barrier against attack.

Here is a link for a bit of further reading Coastal Defence and Fortification

The forts could be modeled after Bastion Forts or star forts.

The medieval artillery would most likely consist of gunpowder cannons.

The ships would also be outfitted cannons.


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