The Greek verb ' (σπένδω), "pour a libation", also "conclude a pact", derives from the Indo-European root ', "make an offering, perform a rite, engage oneself by a ritual act". The noun is " ("plural ")", "libation." In the middle voice, the verb means "enter into an agreement", in the sense that the gods are called to guarantee an action. Blood sacrifice was performed to begin a war; ' marked the conclusion of hostilities, and is often thus used in the sense of "armistice, treaty." The formula "We the polis have made libation" was a declaration of peace or the "Truce of God", which was observed also when the various city-states came together for the Panhellenic Games, the Olympic Games, or the festivals of the Eleusinian Mysteries: this form of libation is "bloodless, gentle, irrevocable, and final".