The 24-hour clock — commonly called military time in the United States — eliminates one specific source of time ambiguity: the AM/PM distinction. "14:00" is unambiguously 2pm in a way that "2:00" is not. For domestic scheduling and everyday communication, this is a genuine improvement.
It does not solve the timezone problem. It does not even address it.
"The deployment is at 14:00" is unambiguous about whether it is morning or afternoon. It is entirely ambiguous about which 14:00 is meant. 14:00 in London and 14:00 in New York are five hours apart. 14:00 in Tokyo and 14:00 in Los Angeles are seventeen hours apart. The 24-hour format carries no timezone information and makes no claim to do so.
The confusion arises because the 24-hour clock is associated with precision — with military, aviation, and medical contexts where ambiguity is unacceptable. This creates an impression that using it is sufficient for unambiguous communication. It is sufficient for AM/PM ambiguity only.
A fully unambiguous time reference requires: the time in 24-hour format, the UTC offset, and a geographic anchor. The 24-hour clock provides the first element. The other two must be added explicitly.
"14:00 UTC+1 (London)" is bulletproof.
"14:00" is not.