Focus on a particular target when attacking/defending
When your units are attacked from several directions, do not fight back to all the directions. Concentrate your counter-attack on the enemy in one direction.
When you attack, use more soldier units than the target enemy.
Once you eliminate the enemy units in one direction, collect your soldier units and focus your attack to another direction.
By repeating this tactic, you can minimize the loss of your soldier units.
This tactic works effectively when you fight on the attacking side, too.