Modern pacifism began early in the 19th cent., with peace societies that were formed in New York (1815), Massachusetts (1815), and Great Britain (1816). Other countries followed, and societies were established in France and Switzerland not long afterward. In 1828 William Ladd, one of the early pacifists, welded the many local societies that had been established in the United States into the American Peace Society. Soon more radical pacifists came to the fore, and the peace movement in the United States became connected with other causes under the leadership of such men as Elihu Burritt and William Lloyd Garrison. However, Garrison later abandoned his pacifism and advocated war to end slavery.
The first international peace congress met in London in 1843, marking the earliest attempt to organize on an international scale. Both the Mexican War and the Crimean War checked development temporarily, and the Civil War completely destroyed for the moment the peace movement in the United States. After the Civil War the movement reappeared in new forms, influenced strongly by the internationalists. The efforts of Frédéric Passy in France and of Sir William Randal Cremer in Great Britain led to the foundation of the Inter-Parliamentary Union in 1892. The International Peace Bureau was founded at Bern, Switzerland in 1892. The award of the Nobel Peace Prize (see Nobel, Alfred Bernhard) did much to encourage pacifist thought. Even the Franco-Prussian and Spanish-American wars did not check the spread of peace agitation.