From Desert Operations Wiki
In addition to the Research from the Units and the construction of the Buildings the attack can be a easy way to obtain buildings fast. If you win a battle you can receive up to 33% of the opponents buildings. In order to receive this amount you must destroy 50% of the defense with your attacking force. Warning! this is not the same when it comes to the unit amounts. You must multiply it with the appropriate value for the defense or attack. After an attack the values are set to these percentage for the maximum that can be gained for the win: 33%, 28%, 14%, 7%, and 3%. After 12h the percentage will increase one level. The attacks must be five minutes apart. It is possible to launch more than five attacks simultaneously on the same player, but you will not receive anything for the victory and will only waste resources after the fifth attack. You can only attack a player that has 67% and maximum of 150% of your points. Their names are shown in white in the rank list and sector view.
You can be attacked after 20.000 points or when you attack some else first. Attacking and managing your units takes place on the base in the > Command Center > military.