Foster was born on 2 March 1836 in Petersburg, Indiana, and raised in Evansville, Indiana, the son of Matthew Watson, an Indiana farmer, and Eleanor Foster (née Johnson). He graduated from the fledgling Indiana University as class valedictorian in 1855, but decided not to become a preacher as his parents hoped. Instead, Foster attended and graduated from Harvard Law School, then moved to Cincinnati, Ohio, to begin his legal career. During the 1960 election he was an abolitionist and Republican go-getter for President Lincoln.
In 1861, Foster volunteered in the Union Army in the American Civil War. Initially commissioned a major, he rose to the rank of colonel, serving with the 25th Indiana Volunteer Infantry, the 65th Indiana Volunteer Mounted Infantry, and the 136th Indiana Volunteer Infantry. Foster’s troops became the first to enter Knoxville, Tennessee, after the successful campaign by General Ambrose Burnside.
Despite his view of war as “the most terrible and futile of human follies,” a perception which apparently dated from his college days at Indiana University, Foster was tempted to remain in the army where the rigors of active campaigning had seemingly strengthened his previously uncertain health. Nor was he oblivious to the excitement of battle. In his account of the bloody struggle at Shiloh, he recalled a number of actions as “grand beyond description.” Of war itself, he readily admitted “a certain glamour.”
Still, unlike a generation of his contemporaries who came to romanticize their wartime experiences and relish the manliness war supposedly ensured, Foster’s occasional flirtation with the glories of the battlefield seemed to lessen rather than intensify with the passing of time. In fact, when his memories of that campaign were published more than half a century later, he claimed that his soldierly experience had “strengthened and confirmed” his opposition to war: “I witnessed the sad effects of the conflict in dividing and embittering brothers of the same blood, the ravages of the battlefield and the hospital, the valuable lives lost and the widows and orphans, the enormous expenditure of money, and the great war debt to be paid by a coming generation.”
After the war, Foster returned to Indiana and (in addition to his legal practice) edited the Evansville Daily Journal. By 1869, after three years as editor, he became postmaster of Evansville and chairman of the Republican State Central Committee of Indiana. For keeping the Hoosier state in the Republican column, successive Republican Presidents Ulysses S. Grant, Rutherford B. Hayes, and James A. Garfield appointed Foster the U.S. Ambassador to Mexico (1873–1880), then to Russia (1880–1881). President Chester A. Arthur made Foster the United States Ambassador to Spain (1883–1885).
When Foster returned to the United States, it was in Washington, D.C. where he established himself for the remainder of his life. In Benjamin Harrison’s administration, Foster served as a State Department “trouble shooter” before becoming Secretary of State for the final six months of Harrison’s term (from 29 June 1892, to 23 February 1893). As Secretary of State, Foster helped direct the overthrow of the Hawaiian monarchy.
After leaving public office, Foster remained in Washington and invented a new type of legal practice, lobbying for large corporations seeking favors in Washington and chances to expand abroad. Foster also used his government and political contacts to secure legal fees as counsel to several foreign legations. He also continued to serve Presidents part-time on diplomatic missions. As such, Foster negotiated trade agreements with eight countries, brokered a treaty with Britain and Russia concerning seal hunting in the Bering Sea, and negotiated the Treaty of Shimonoseki of 1895 (technically as legal consultant and commissioner for the Qing Dynasty) in which China recognized Korean independence as well as ceded Taiwan to the victorious Japanese after the First Sino-Japanese War.
In 1903, Foster published American diplomacy in the Orient, followed in 1904 by Arbitration and the Hague Court. In 1906, he wrote The practice of diplomacy as illustrated in the foreign relations of the United States.
Foster died in Washington, D.C. on 15 November 1917. His body was returned to Evansville, Indiana, where it remains in Oak Hill Cemetery.
His daughter Edith Foster married Presbyterian minister Allen Macy Dulles, and their children included John Foster Dulles (who also became a U.S. Secretary of State) and Allen Welsh Dulles (later Director of Central Intelligence). Foster’s daughter Eleanor married State Department legal advisor Robert Lansing (who later also served as U.S. Secretary of State); their daughter Eleanor Lansing Dulles became an economist and diplomat. Foster is also the great-grandfather of the noted Catholic convert and theologian Cardinal Avery Dulles.