The so-called American civil religion entails the belief that the United States is God's chosen nation—the New Israel—and that the military is the instrument of God's will. According to its precepts, if the American people reject sin and willingly sacrifice their own self interest for the common good (especially during times of war), God will reward the nation with victory and prosperity. The military's use of civil religion complements rather than replaces denominational faiths and serves an important unifying function. Such was the case during the Revolutionary War when both Congregational and Presbyterian churches supported the patriot cause with their financial and spiritual resources. Employing biblical ideology, clergy also greatly strengthened the will to fight by calling for Americans, God's chosen people; to throw off their English bondage (Egyptian bondage, in the biblical narrative) and create a new nation based on divine principles as had the Israelites of the Old Testament.
Religious nationalism continued to play a crucial role in the new republic's military affairs following the Revolutionary War. While early legislation regarding the armed forces did not specifically mention religion, the founding elite considered patriotic faith an essential component of the citizen-soldier concept. According to the Uniform Militia Act of 1792, the United States could avoid the dangers to liberty created by a large standing army by requiring all able-bodied males to train with militias while the national government maintained a small regular army to patrol the frontier. During hostilities, according to the theory behind the legislation, the army would expand with citizen-soldiers who would sacrifice their own self interest to volunteer for military service.
Because American defenses would depend on the civic virtue of the American citizen—values that national leaders believed the public lacked—the military (along with the family, church, law, press, and free public education) would need to instill the requisite masculinity, personal morality, patriotism, and self-sacrifice into the national psyche. While civic virtue is not necessarily related to spirituality, the armed forces found organized religion and religious nationalism the most effective means to communicate to the American people the values it believed necessary for national defense.
Historically, once war is declared, American churches have rallied to the battle flag. Such was the case during the Civil War when denominations (some of which had already split North and South over slavery) supported their respective sections with patriotic fervor. While northern churches were nearly unified in their support of the Union, all of them did not advocate freeing the slaves at the beginning of the conflict. Those congregations generally reversed their position, however, after the Emancipation Proclamation gave the war a holy cause. The notable exception to northern religious solidarity was a number of pacifist faiths, including the Society of Friends (Quakers) and Mennonites, who opposed war in general. Most Quakers refused to fight but many did serve in medical roles and were instrumental in educating the recently freed slaves. A variety of Christian benevolent societies, such as the Young Men's ...