Decide what a settlement defends against before building anything, and design for the middle threat, armed groups of 5-20 people, because most post-collapse violence comes from opportunistic groups and not organised armies. Rank every threat by probability times impact, since a likelier and deadlier danger such as fire or contaminated water may outrank raiders, and make sure no defence adds a danger worse than the one it answers.
Part of Defensive Architecture
Threat assessment is the step of listing what could harm a settlement, how likely and how bad each is, and choosing defences in proportion; the design response is the set of buildings and features that follow from it.
Fortification Costs Labour, Secrecy And Safety, So It Is Sized To The Threat
The defensive-architecture guide opens with the trade: in a stable society defence is unnecessary, in a collapse it may decide whether a settlement thrives or is looted, but fortification costs labour, materials and community psychology, and a settlement that looks like a fortress signals that it has something worth taking. It sorts threats by size. One to five people (thieves, desperate scavengers) are deterred by strong doors, alert dogs and a night watch, with no fortification. Five to twenty (bandits, raiders) are deterred by visible community strength, controlled access and hardened refuge points; moderate fortification works. Twenty or more is a military-style threat, and fortification only buys time: diplomacy, alliances or relocation have to do the real work. Hence the rule to design for the middle threat and to make the settlement harder to attack than the next one.
Worked Example: Ranking Defence Against Other Dangers
The ranking method of the household threat guide multiplies probability by impact, each scored 1 to 5, and acts at once on 15 or more, within the week on 8 to 14 (Priority Ranking). The scores below are invented for a settlement to show the method; score your own.
| Threat | Probability | Impact | Score | Action |
|---|---|---|---|---|
| Contaminated water | 4 | 5 | 20 | Act now |
| Settlement fire | 3 | 5 | 15 | Act now |
| Armed group of 5-20 | 2 | 4 | 8 | Plan this week |
| Thieves or scavengers | 3 | 2 | 6 | Watch, dogs, doors |
| Group of 20 or more | 1 | 5 | 5 | Diplomacy, alliances |
- Fire scores 3 × 5 = 15, which is above raiders at 2 × 4 = 8.
- A defence that blocks exits raises the fire score: a barred hall with one door that moves the probability from 3 to 4 makes it 4 × 5 = 20, level with contaminated water.
So the defences in this guide must be checked against the fire guide before they are built (Fire Prevention in Settlements).
What You Need
- A written threat list by the three groups of the household guide: animals, environment, people (Threat Categories)
- Scores for probability and impact, agreed by the settlement’s council
- A site walk at 50, 200 and 500 m for approaches and dead ground (Local Terrain Analysis)
- A date for re-scoring, since scores go stale
Method: From List To Design
Step 1: List the threats, including the quiet ones.
Step 2: Score and rank them.
Step 3: For each action-level threat, pick the cheapest response that works.
Step 4: For the human threat, apply the size tiers: doors, dogs and watch for the smallest; layers, hardened refuge and controlled access for the middle; alliances for the largest (Layers of Defense Concept).
Step 5: Check each defence against fire, flood and exit safety before building.
Step 6: Re-score each season.
Common Mistakes
- Designing for the worst threat. It exhausts the labour that food and water need.
- Looking like a fortress. It attracts the attention it is meant to avoid.
- Defending against raiders and ignoring water. The quiet threats kill first.
- Hardening that traps your own people (see Safety).
Safety
Every barred door is also a trap
A drop bar is sound on a dwelling, where the few occupants lift it. On the exit of a hall, a workshop or any room that can hold a crowd it is a crush mechanism, because a bar cannot be lifted against a press of bodies and in a fire that is the press you get. Any room holding more than a handful exits outward by pushing, with nothing to work first. Secure such a building from outside when it is empty.
What’s Next
- Learn next: Threat Categories & Likely Scenarios — what each size of group actually does
- Combine with: Cost-Benefit of Fortification — pricing the response