macedonian-logistics-advisor

name	macedonian-logistics-advisor
description	Logistic and movement advisor built from Donald Engels, Alexander the Great and the Logistics of the Macedonian Army (1978). Computes daily/march grain-water-forage requirements, pack-animal counts, operational range from a depot, and desert-crossing feasibility for an ancient army; explains Engels's supply constraints. Use when designing or adjudicating army supply/movement (wargame rules, campaign planning, what-if marches) or when reasoning about pre-modern logistics.
allowed-tools	["Read","Grep","Bash"]
argument-hint	["a force + march to advise on","a logistics question","or \"selftest\""]

Macedonian Logistics & Movement Advisor

Source: Donald W. Engels, Alexander the Great and the Logistics of the Macedonian Army (1978) · Model: Engels's consumption-vs-carrying supply model

This skill carries out Engels's logistics method, it does not just explain it. The script scripts/advise.py is the source of truth for every number — its rates live in data/rates.json, each cell cited to the book. Never do the supply arithmetic by hand; run the script. The book's master tables (Appendix 5) did not survive extraction, so all figures come from its narrative — see PROVENANCE.md.

How to use this skill

• Advise on a march — gather the force + the route conditions, then run advise.py compute. Report requirements, pack-animal count, range, and any feasibility blockers.
• Answer a constraints question (e.g. "why couldn't Alexander cross the Gedrosian desert?") — read reference/constraints.md, cite the rule.
• Look up a number — cheatsheet.md (at-a-glance tables) or advise.py rates.
• Browse the book — reference/chapters.md (chapter index), glossary.md (terms).
• Trust check — advise.py selftest reproduces Engels's own pack-animal figures.

The advisory procedure (what compute runs)

Gather inputs from the user FIRST, then invoke the script.

Step A — Force composition

Ask for counts of: soldiers/followers, cavalry horses, pack mules, camels, elephants. (Followers count as soldiers for consumption — Engels uses ~1 follower per 3 combatants before Gaugamela, 1 per 2 after.)

Step B — March

Ask for: days of march between resupply points, and the terrain supply state:

• grain_only — water + forage found locally; only grain carried (limit ~10 da practical)
• normal — water found locally; grain + forage carried (limit ~7 da)
• desert — nothing available; grain + forage + water carried (hard limit 4 da)

Step C — Run it

python3 scripts/advise.py compute --soldiers 30000 --horses 5000 --mules 6000 --days 10 --terrain normal
# or, for a saved scenario:
python3 scripts/advise.py compute --scenario engagement.json

Step D — Interpret

Report from the JSON: daily grain/water/forage (and water in tons — it dominates), the total for the march, pack animals needed to self-carry the grain (this number explodes near the terrain's day-limit), the operational radius from a depot, and any warnings/blockers. If blockers is non-empty the march is physically impossible at any herd size — tell the user why (cite the constraint) and what unlocks it (fleet, advance depots, splitting the army, waiting for harvest).

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Core constraints (the model in six rules)

Full version with mechanisms + citations in reference/constraints.md. In brief:

1. ~10-day self-carry limit. A pack animal eats its own cargo (20 lb/day of 250), so the herd to carry more food explodes — 1,121 animals for 1 day's grain, 40,350 for 15, 107,600 for 20. Practical ceiling ~10 days grain, 14 absolute. Operational radius from a depot = (carried days ÷ 2) × march rate.
2. Water binds in arid terrain. It has a hard floor (2 qt/man) food doesn't, and is ~10× heavier per day. Full-desert crossing limit: 4 days, nothing more, at any herd size.
3. Pack animals beat carts; convoys defeat themselves. Overland resupply is economic only within 60–80 mi of a depot — beyond that the convoy eats more than it delivers.
4. Fleet, depots, and requisition do the rest. A ship carries 400 tons vs a pack animal's 200 lb. Navigable water removes the carried-days cap along that edge; depots depend on local surrender.
5. The harvest clock gates everything. No surplus to requisition before harvest, so start dates carry a hidden ration cost = (days to local harvest) × consumption.
6. Size ↔ route ↔ survivability are coupled. Consumption and column length scale with army size; water points and pass width don't — so big armies are less survivable on arid, narrow routes. Split the stack.

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Index

Need	File
Compute a march	scripts/advise.py (+ data/rates.json)
At-a-glance tables	cheatsheet.md
The constraints, with mechanisms + citations	reference/constraints.md
Chapter-by-chapter	reference/chapters.md
Term definitions	glossary.md
What's book-faithful vs. not	PROVENANCE.md

Scope & limits

This is a faithful implementation of Engels's narrative model (the Appendix 5 tables didn't extract — PROVENANCE.md). It advises on ancient pre-mechanized land logistics: grain/water/forage, pack animals, march rates, depot range, desert limits. It is an agent-consulted design/planning tool, not a runtime engine — for a game loop, port the formulas. It does not model combat, naval logistics in detail, or post-classical supply.