"Peace without victory" refers to Woodrow Wilson's attempts to advocate for a peaceful solution to World War I. Wilson made the speech in January of 1917, but his appeal was not heeded, and the United States declared war against Germany only two short months later.
Wilson, the 28th President of the United States, was in the Civil War era and had seen the destruction that massive warfare brought. It was crucial to his political campaigning to keep the United States out of the war that was ravaging Europe. In the "peace without victory" speech, he pointed out that each side of the conflict had expressed at least some willingness to discuss terms of peace without surrendering. Rather than join the war, Wilson idealistically called for the United States to be a peacemaker, applying its power along with other nations to the cause of preventing a war of this scale from ever happening again.
Wilson's argument called this an extension of the Monroe doctrine of non-interference, where for over a century the United States had avoided entanglement in European conflicts (and demanded in return that European powers similarly leave the Americas alone). He believed that each nation should be left in peace to govern itself, and that this could only be achieved by a universal agreement to limit military power, keep the oceans free and open to all and avoid the military alliances which had turned World War I into a global conflict.