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Open Strategy Games

A reference for faction-scale, argument-driven play

📖 Learn

Read the Open Strategy Games Handbook — the complete guide to running and designing OSG sessions.

⚔️ Play

Contested Ground is a ready-to-use rules framework built on the OSG format.

📋 Log

Factionlog is the standard notation for recording OSG session events.

Open Strategy Games are faction-scale, argument-driven games where players control organisations rather than individuals, resolve conflict through reasoned argument and probability, and build shared history through play.

The Open Strategy Game format was defined by Chris McDowall, originating in the Matrix Game tradition established by Chris Engle and Tom Mouat. Logo by Delapouite under CC BY 3.0.