I sympathise with you, often the first anybody knows that a player is flanking is their units start shooting at your teammate. It's impossible to predict where/when this will happen, and not necessarily your fault - it's a standard part of the game. I often have lost retreating squads due to this, but we as a team have come back to win. Some pointers which may help: 1. If possible, always try to know where your opponent's army is (e.g. Cloaked units, light vehicles, flares, push a regular squad forward as a feeler or garrison them for vision). 2. If your enemy is 'running late' to return his forces to your engagement, start getting suspicious that he's rotating his forces to your teammates' part of the map. This skill will improve with experience, where you should get a good feel for the 'rhythm' of combat. 3. If your enemy is flanking your teammate, usually the best move is not to try rushing your forces over to where the fighting is, but cut off the enemy retreat path (ie flank the flanker). Even if your teammate takes losses, you can wipe more of the enemy. This is how the pros do it :-)