To add to the other answers about infantry placement. Think about where you don't want the infantry. If in front of the battery the infantry could be hit by sabots or fused rounds that go off prematurely. Behind the battery, the battery masks the fire of the infantry. Both in front and behind the battery gives the enemy a greater chance to hit something with short or long rounds. Having said this different elevations of infantry and battery could make a difference on placement in front or behind.