A-ha. Here's the real scoop at last. It turns out that the speaker and the other guy were enemies in a war.
And when they were "ranged as infantry," or lined up in ranks for battle, they could totally look right at each other.
Awkward? Yes. Actually, try horrifying. Since they're standing face to face, we know that they're on opposite sides of the fight. Which also means they won't be drinking buddies anytime soon.
The fact that they're infantry tells us something interesting, too: these dudes are low on the military totem pole. Usually, it's the infantry who die in the largest numbers, because they're following orders from the higher-ups.