It contrasts "foe and friend," just as the sonnet contrasts "love and hate."
We are natural enemies; and when your foe is disabled, then is the time to strike.
By this time, the first of August, we knew more about the foe we were to meet.
They lie at the mercy of every foe, of every passion, of every change.
You were friendless, and the man who has all earth for a foe befriends you.
Ignorant of the law—the law only seemed to him, as it ever does to the ignorant and the friendless—a Foe.
And had I been as much your foe, as you imagine, you had not perhaps been here now.
All seemed eagerly awaiting the command to rush against the foe.
He was daily worse fed, and as the weeks went by was daily less able to crush a foe.
We have made such treaty as never yet was made between foe and foe.