You can easily defeat any infantry from i.e.(archers to wood raiders)
using your Arbalests. To accomplish this you must build an archery range.
Then research the archer to crossbowman and then to arbalest.Then reasearchall 
archery reasearchs in blacksmith and archery range.These Arbalests, when fully 
researched are extremely powerful in range attack and somewhat weak in combat. 
Just create 20 arbalests, Double-Click any one to select all of them and just 
Right-Click to attack any enemy infantry or cavalry.It will take time to kill 
battering,capped and siege rams;cavarly.When they will come nearer to attack 
the enemy infantry attack the arbalests. 
Since the arbalests are more in number the enemy infantry will die 
on their way when trying to reach our men. The arbalests have very long range 
so that they can easily kill the infantry and siege units. If they (enemies) 
follow this technique it will be a problem to you so you haveto be quicker. 
If more doubts persists, Mail me.

Tip:you will atlaest 36 to destroy a castle.this doesn't work on longbowmen
(english unique unit).