In game no one knows now, but I can give some idea about how battles were usually won in reality based on traditional Chinese books about military / Arts of wars if you may.
The first thing they stress about the most .. is the will to fight. Troops are only useful if they are willing to fight / willing to die. If they lose that, they are as useless as a pile of dead people. I think the battle of Issus of Alexander demonstrated this clearly. He won not by killing troops, but make the Persian King lose the will to fight, and the army lose the same thing when they saw their King ran. I got some Chinese examples too, but I bet you guys never heard of them. In Sun Tzu Art of War, he deliberately said that, a good general has to gather his men and throw them into a risky situation. Show your men running is not an option. Put yourself into a dead end, and you will come out alive. The exact quote in traditional Chinese from 2 separated paragraphs: "聚三軍之眾, 投之於險, 此謂將軍之事" and "投之亡地然後存, 陷之死地然後生。 夫眾陷於害, 然後能為勝敗". One of the most famous battles to support this logic is the Battle of Julu.
http://en.wikipedia.org/wiki/Battle_of_Julu for your reference... it is quite accurate. This happened after Qin unified China from the warring state period. What Xiang Yu did was simply threw his whole army into a no escape situation. They cross the river before the main battle. Xiang Yu ordered everyone to destroy their cooking tools, sink all the ships they used, and only bring 3 days of supplies with them. Without the hope of survive by deserting, even Xiang Yu's troops are outnumbered, his men fight so fiercely that the professional Qin's army are overcame.
Only when both sides have the will to fight, other factors come into play. If your man can form a testudo, but would run the moment they contact with the enemy, no formation / weapons and equipments can save the day. That is why supplies are SOOOOOOOOOO important, cuz no one will stand the line when they know that they will starve to death after risking their lives. A lot of victories in Chinese history were won by breaking the enemy's will to fight. Even Alexander has to stop his conquest when he knew his men are wishing to go back home. I am quite sure you guys can draw quite some examples from your history books.