H hour, also known as the "hour of execution", refers to the specific time when a military operation or attack is supposed to occur. While H hour is a widely recognized term among military personnel and strategists, there are several synonyms that can be used to convey the same meaning. Some of these include "zero hour", "D-Day", "invocation", "countdown", and "launch time". These words are commonly used in military and strategic discussions to indicate the time when the plan or operation is scheduled to commence. Regardless of the synonym used, all indicate the importance of timely execution in any military operation or attack.