The critical moment when a planned operation begins, especially a military attack or important mission. It refers to the exact time when decisive action is scheduled to commence.
This military term originated during World War I, when 'H-Hour' designated the hour of attack and was counted backward as 'H minus 1,' 'H minus 2,' etc. Zero hour represented the moment when the countdown reached zero and the operation began.
The phrase reflects the military's precision with timing, where synchronization could mean the difference between success and catastrophe. Interestingly, while 'zero hour' suggests finality, military planners often built in flexibility, knowing that the actual moment might shift based on conditions - making 'zero hour' somewhat paradoxically fluid.
Complete word intelligence in one call. Free tier — 50 lookups/day.