Cyclic, so you'll know who attacks first.
Offense killrate and defensive killrate are close, but offensive is sleightly heigher.
With some math/experience you can see that attacking with 40,44,47,50 and some higher numbers gives the attacker advantage of 1 army, which is winning.
It also seams like the attack with 44 benefits from a rounding error. (since defending with 45, should kill 31,5=32 armies, but kills 31 instead as can be seen in turn 17 of http://warlight.net/MultiPlayer?GameID=5212664
So you win this game if you reach 41,45,48,51 armies on the attack. If you reach anything in between on the attack you must attack with all armies and try again.
I'm not sure if i made it clear, but you can see most of it by browsing through bobs games
Edited 2/19/2014 16:28:48