Military peaks of major powers

[Hamburger]

A spin off from a Backroom discussion, which may be better discussed or answered here. What were the peaks of their respective armies of major powers in history? I'll start with the ones I nominated. Peaks are relative to their era.

Russia: Manchurian campaign, 1945
US: Gulf War 1, 1991
Britain: Hundred days, 1918
Germany: Barbarossa, 1941

Others:
France: Napoleonic wars?
Mongolia: Mongke's reign?

Germany was at high peaks in 1942 it was the last year of their successions.
Russia better say in 1960s.
France, Definitely in Napoleon wars.
Persians and Iranians in General (with all its ethnics and tribes) at times of Darius(h) The Great.
Also Ottomon Empire at times of Sultan Suleyman The magnificent.
but i think Mongolians were the largest empire ever existed in history then Russia. but Mongolians had many Civilized and wealthy conquered lands which russia did not.

from 1800s to 1917-1939 Great Britain.

and now........Definitely US of A !!