Waiting is bad. Always quickly re-assume your attitudes to both sides, cut the enemies down as they advance, crushing them in the direction from which they attack. Whatever you do, you must drive the enemy together, as if tying a line of fishes, and when they are seen to be piled up, cut them down strongly without giving them room to move.
The idea here is simple and is almost identical to the military term Enfilade.
A formation or position is “in enfilade” if weapons fire can be directed along its longest axis. For instance, a trench is enfiladed if the opponent can fire down the length of the trench. A column of marching troops is enfiladed if fired on from the front or rear such that the projectiles travel the length of the column. A rank or line of advancing troops is enfiladed if fired on from the side (flank).
The benefit of enfilading an enemy formation is that, by firing along the long axis, it is easier to hit individual troops within that formation. Adjusting the elevation of the weapon merely directs the fire to a different point along the axis of the formation, although traversing the weapon is more likely to result in a miss. Enfilade fire takes advantage of the fact that aiming at a target is easier than correctly estimating the range to avoid shooting too long or short. Finally, projectiles that miss an intended target are more likely to hit a different target within the formation if firing along the long axis.
To “dumb it down” for you. What this means is that it’s not ideal when your enemies are spread out so that you have to direct fire at each one in turn. If they are, you will have to “traverse”, better known as moving from left to right (or vice versa), to shoot at the other targets. If you miss nobody else in the enemy formation is going to be too concerned and as you are shooting at one all the rest are able to maneuver, find cover, and shoot back at you.
If you are lucky and the enemy is lined up “enfilade” to you things are tilted in your favor. If you miss your target, or have a weapon with enough juice to punch clean through, there may be another unlucky sap over there that you will hit. All you have to do to engage this cluster of enemy is change the “elevation” (move your sights up or down) of your fire.
An idea to toss around in your head is exactly how you can catch the enemy in this situation.
You may just be lucky and catch them napping, you could “channel” your opponents by placing obstacles like wire or minefields, or you can take advantage of positioning yourself so that features like trenches, streets, hallways and other features that “line em up” can do the work for you.
Conversely, remember that THEY are looking to this exact same thing to YOU!