Brethren and Mennonites are diverse and complex bodies with long interconnected histories. Some historians have argued that religious radicals, such as Mennonites and Brethren, were the essential shapers of the distinctive contours of American Christianity. The Brethren–Mennonite sibling rivalry has often been intense. But during times of stress, such as war, they have worked together, often along with Quakers. In America, they have both been creators and products of a culture that has occasionally persecuted them but has more often romanticized and idealized their attempts to serve Christ and their neighbors.