J.T. said:
That's a little hard when you can't win a battle to initiate a siege.
You can start plenty of sieges even when always running away. Just don't attack anywhere the enemy has an army.
I know what you're complaining of, though. It appears that the AIs/rebels get a pretty nice bonus in battle. My guess is that for the first roll only, they get about a +2 or so. (After the first days of battle, I think it is fair, but by that time your morale is often shot.)
You can always win with vastly superior tech and morale, and that's what the people above are talking about getting. But, obviously one does not always have that.
So, to win battles, here's a few pointers.
First, you need to understand the battle system. There is randomness in battles, but it happens only every 5 days. So, the first roll that happens has its effects imposed over 5 days, but you can see what it is (more or less) after the first day of battle. It is highly important, esp w/ the AI bonus I think is there, to
observe the first day of battle and flee that battle if the first result is at all against you. You should really only fight one major battle at a time, and pause every day while you watch results. When the reroll happens for day 5, again you want to flee if the thing turns against you.
Second, know how to get bonuses, and only fight with them. DP settings, leaders, 2x the cavalry in plains/desert, and defense across rivers are the main ones to look for. Only engage the enemy with bonuses -- if you don't have them, maybe do one day of battle (to see if you get lucky) and flee, or even just flee outright. Try to get Offensive 9 (in the early game; until about 1500 or so), and Quality 9 (after land 9), as soon as possible.
Third, make up for all the battles you lose by (a) killing lots of small armies immediately upon their recruitment, when their morale is low, and winning is easy, or (b) getting 100% warscore. If you will get 100% warscore anyway, it does not matter how many battles you flee.