For ten points, name this concept that is often contrasted with war.
Marsilius of Padua wrote a book titled for the  Defender of this concept. A movement entitled for the Truce and this concept of God succeeded in limiting the days on which Catholic polities could fight, and Alexander Mackenzie traveled up a river named for (*)  this concept to reach the Continental Divide. This concept was enforced in the Holy Roman Empire during periods of  Landfriede. George McClellan led a branch of the Democratic Party named for this concept, and a Bolshevik slogan paired it with "Land and Bread". For ten points, name this concept that is often contrasted with war.
Marsilius of Padua wrote a book titled for the  Defender of this concept.
Peace