Complex sentence: Not all Quakers embrace this testimony as an absolute; for example, there were Friends that fought in World War I and World War II. Some others were firm have testified to peace have included vegetarianism and a commitment to restorative justice.
Split into simpler sentences: Not all Quakers embrace this testimony as an absolute; for example, there were Friends that fought in World War I and World War II. Some others were firm pacifists. Apart from the specific question of war, other ways in which Friends have testified to peace have included vegetarianism and a commitment to restorative justice.