Best case - you'll lose some men in the coming battles an the upkeep will reduce. If you're taking on a mission to escort someone, resolve a dispute, or take out bandits, be sure to bulk up on recruits, even if the upkeep is a lot. It's better to over-prepare than under-prepare.Once you start fighting other factions, expect them to use plenty of tactical maneuvers on you!.
Once you get the hang of things, try practicing maneuvers against opponents you know you can beat to see how to position your infantry and archers, while having cavalry follow you on flanking runs. Tactical commands can be daunting for new players - but don't worry, bandits don't have tactics either, they'll always charge straight at you.Cut your teeth on small bandit parties until you're ready to join a faction, and then follow them into war against other teams. When first starting out, don't try to play gutsy and attack caravans and villages just yet - or you'll get factions pissed at you long before you're in a good position to take sides or hold your own against an army.You can only carry so many weapons into battle, so make sure you have the right stuff equipped for the right scenarios (don't take lances into bandit hideouts, or short weapons with no reach on a huge cavalry charge).If your enemy won't let you get an attack through, press E to kick or shield bash to break their defense.Combat can be tricky to get the hang of for new players - you'll need to get used to seeing which way an enemy is preparing to strike and react accordingly to block - and keep yourself from getting overwhelmed whenever possible.
Sometimes if your speed is almost even, it will take forever to chase them down unless they're also looking for a fight - and waste valuable time, or let them regroup with others to bolster their numbers before turning to face you.