two generals problem conceptpaper
Two armies must coordinate an attack across enemy territory using messengers who may not arrive.
Two armies must coordinate an attack across enemy territory using messengers who may not arrive. No protocol can guarantee both will attack: every message needs an ack, the ack needs an ack, infinite regress. Foundational impossibility result for reliable agreement over an unreliable channel. Real distributed systems work around it with timeouts and probabilistic guarantees rather than absolute certainty.