I'm interested in history, but I don't study it. What I know of battle probably all comes from choreographed scenes in films and TV programmes, where each man fights another man and occasionally one man is free to save a friend from mortal injury.
But what I've always been curious about is what was it actually like to be on a battlefield, with a sword or shield or whatever, and fighting? Were there minor tactics at that stage or was it a rumble? Did the men at the back have to wait for the men at the front to fall, or could they charge past and pick out their own combatant? Were one-on-one matches over in seconds or could two men with swords work on each other for many minutes? Was it a deafening roar or was it eerily quiet save for the sound of metal upon metal? Were men who were wounded but not dead, left to live out their days disabled, or was there not that level of honour? Did all units go in at once, or were some kept back to replace the tired ones later on? Would a man rest for 10 minutes before going back in, or was it non-stop, til you drop, sort of stuff? Etc.
I know some factors will be culture-based and each battle different, but I'm assuming the basics of battle didn't change for hundreds of years. I'd also be interested in reading some good true first-hand accounts, if anyone knows any. Are there any unusual stories about things that happened on the battlefield?
I think this is still an open question. Probably all of what you suggest happened at some point, but it doesn't appear that men could handle hours and hours of sustained fighting. So men wouldn't have been hacking at each other all day without rest. The Iliad seems to suggest warriors might fight for a time, then hop back on their chariot to ride away and rest. Here is a show that tests the ability to fight in plate armor. So it doesn't look like warriors would be in the melee all day long. As to how exactly the knights were given a chance to rest, I don't know. Probably a lot of that depends on how they were organized.
You might check out the story of Titus Pullo and Lucius Vorenus for how soldiers switch of attacking. But take what Julius Caesar says with a grain of salt.