When two armies are fighting each other, and then reinforcements arrive for one of them, did they take the time to deploy in battle formation? Or did they attack in the column formation they were marching in?
I know for cavalry it's easy to spread out because of their speed and there wasn't usually that many of them (generally speaking), but what about 10s of thousands of infantry? I would assume that if your allies were about to be routed, you would try and turn the tide as quickly as possible. Or did their mere presence stop any thought of routing?
This is one of those shower thoughts that any fan of history usually gets.
Strange-Ad1209 t1_ix00xs2 wrote
During most wars of the 20th and 21st century replacements were sent forward to join units on supply trucks or helicopters. They were rarely sent forward as formed units as they were replacements for personnel lost in formed units along the FEBA. Now Combat units were sent to the Forward Edge of the Battle Area to enhance the combat units already deployed but that was usually when formations were in Movement to Contact and not yet engaged. It all actually depends on the tactical situation as to how personnel get deployed from a staging base.