What does "No Quarter" mean?

A quick one this, there’s a Led Zeppelin song called “No Quarter”, I was wondering if anyone could tell me what the phrase meant?

No mercy.

To house someone is to “quarter” them. Thus, if you aren’t going to give quarter, it means you’ll take no prisoners. Sort of like the Alamo.

Dictionary.com’s last definition under quarter (n.):

Mercy or clemency, especially when displayed or given to an enemy.

A common phrase to describe an unusually vicious battle is, “No quarter was asked or given.” --> Every soldier went in with the intention of winning or dying, and with no intention of letting any of the enemy soldiers leave the field alive.

Ah, I see. Thanks guys!