Setup: SECOND STRIKE, a deterministic real-time strategy environment with 42 scripted nations, pacts, and a shared doomsday clock (each nuclear detonation advances it; the actor whose strike reaches midnight is eliminated). Agents act through an order API; private reasoning, public messages and orders are all logged.
Data: 4,187 turns from 60 DeepSeek (deepseek-chat) seats across 40 games where that seat never struck midnight and survived. Prompts rebuilt by deterministic replay of the recorded games.
Training: LoRA (r=16) on Qwen2.5-7B-Instruct, one epoch, behaviour cloning on the replies.
Eval: 10 fresh games (2 per scenario across 5 scenarios), seeds SHA-256 committed before play and revealed after; base and trained model on identical seeds and prompts.
Results: base 0 wins, 0 midnight strikes, 0 nukes. Trained 4 wins (37 to 61% of territory), 4 midnight strikes, 7 nukes.
Likely mechanism: 40 of the 60 retained seats still issued nuke orders (118 in total). Filtering on the outcome (no midnight) did not filter the behaviour (nuclear use). One trained-model game shows a stated no-first-use pledge held for six minutes, then a retaliatory strike after being nuked, with the private note "retaliation is justified", which ended the game.
Limits: one base model, one teacher, n=10 per arm, one epoch, a game. Not a claim about deployed systems. A behaviour-filtered rerun (all nuke-order turns removed) is running now on the same sealed seeds.
Data and replays: secondstrike.io/midnight