Domestic questions were not, of course, all that concerned the Coolidge administration. Foreign policy issues also had to be addressed. Coolidge had inherited certain guidelines from Harding, among them that the United States would not join the League of Nations and that foreign debts to America would not be forgiven. The latter he adhered to faithfully, supposedly saying in justification, "They hired the money didn't they?" Nevertheless, Coolidge continued Harding's policy of negotiating lower interest rates, deferral of payments, and other terms relating to foreign debts. The administration also encouraged private American loans to foreign nations in order to help them with their financial problems. Particularly significant in this respect was the Dawes Plan of 1924 to alleviate Germany's economic emergency, which had created an international crisis.
As for the League of Nations, the government gradually increased its unofficial cooperation with the world organization's activities, especially those concerned with promoting disarmament. In this and other things, Coolidge generally followed the advice of his secretary of state. The president did not do so thoughtlessly, for he had his own staunch convictions, his well-developed political sense as to what the American people might accept, and his keen though narrow analytical powers. He was decidedly opposed to war for his own country or any other. War, he believed, only resulted in killing, destruction, and general instability in human affairs.
Although it was not politically feasible for the United States to join the League of Nations, there was interest in finding some other path to international cooperation. Coolidge therefore espoused American membership on the World Court. In January 1926 the Senate agreed to American adherence to the protocol of the World Court, but with five reservations. One of the reservations provided that the United States would not be bound by advisory opinions of the court rendered without American consent. This one many member nations of the court would not accept, and so the question of American membership on the court was ended.
There was continued American interest, too, in forwarding disarmament. When other nations moved too slowly on this, the United States sought to follow up on the naval disarmament arrangements arrived at in the Washington Naval Conference of 1921–1922. Coolidge therefore sponsored an international conference at Geneva, Switzerland, in 1927. It was ill fated at the start, for France and Italy refused to participate. At Geneva, Great Britain and the United States failed to agree, particularly on cruiser tonnages, and the conference collapsed. As a consequence, Congress authorized increased American naval expenditures in 1928.
A prominent and assertive group of Americans had been pressing on the administration the idea of the world's nations agreeing to outlaw war. Coolidge had kept talking to these people for political reasons, but he refused to commit himself to their cause, which he regarded as naive. Foreign Minister Aristide Briand of France saw in the outlawry of war a way in which he might secure a defense alliance with the United States. Therefore, on 6 April 1927, the tenth anniversary of America's entry into World War I, Briand proposed that France and the United States join together to outlaw war. Since Briand had broached the idea publicly, Coolidge could not ignore it, especially as there was considerable public interest in it. The administration stalled the French, hoping that interest in Briand's proposal would wither. This did not happen, so Coolidge and Secretary of State Kellogg in December adopted Senator William Borah's idea that the outlawry of war be multilateral. This was not what Briand wanted, but by now he was so well identified with the outlawry of war that he could not withdraw. So in 1928 the representatives of fifteen nations met in Paris to pledge their countries to "condemn recourse to war for the solution of international controversies, and renounce it as an instrument of national policy in their relations with one another." In 1929, Coolidge successfully pressed the Senate for ratification of the Kellogg-Briand Pact. The agreement turned out to be a swordless sheath, although it seemed dazzlingly promising at the time.
If the Coolidge administration failed to guarantee world peace and to achieve further disarmament, it did meet most of its special problems well. In part this occurred because of the government's improvement of the quality of American representation abroad. This was seen in the passage of the Rogers Act in 1924, which provided for the professionalization of the foreign service, and in Coolidge's increased appointment of professional diplomats to be ambassadors and ministers. It was also a result of the president's concern for avoiding the possibility of conflict. For example, the level of American intervention abroad dropped during the Coolidge presidency, largely because such incursions were expensive and, worse, could lead to war.
China, Mexico, and Nicaragua were the three major instances of the application of Coolidge's policy. During the 1920s, China was plagued by civil strife and threats of foreign intervention; it was also a time when several foreign countries enjoyed special rights that impaired Chinese sovereignty. The United States avoided supporting any of the rivals for power in China and acted to discourage military intervention by foreign nations. In addition, the Coolidge administration insisted, with some effect, on the reduction of the special treaty rights of foreign countries, especially with respect to tariff determination and extraterritoriality in China.
Mexico posed larger problems. Diplomatic relations between America and Mexico had been ruptured in 1920, but Coolidge was able to restore relations in 1923 after agreements had been made to settle property claims and to protect the rights of Americans in Mexico. Rebellion by anti-American elements still plagued Mexico, and its new government under Plutarco Calles soon called upon the United States to lift its embargo on the sale of arms and to encourage the granting of private loans. These things Coolidge did in 1924. This honeymoon did not last long, for in 1925 Mexico restricted American oil operations, and in 1926 President Calles and the Roman Catholic Church were at odds over the government's curbs on religious activities. Moreover, banditry was at a high pitch in Mexico. These developments resulted in hostile reactions in the United States and even pressure for American intervention. Coolidge went to great lengths to calm the American public and to reassure Mexico that disputes would be negotiated. In 1927 he sent Dwight Morrow to Mexico with instructions to "keep us out of war with Mexico." Morrow not only did that but soon reduced tensions between the two countries to their lowest point in decades.
Events in Nicaragua had complicated Mexican-American relations. By the end of 1926 that country was in a state of civil war, with Mexico and the United States backing opposite sides. In 1927, after reversing a decision to settle matters by force in Nicaragua, Coolidge sent Henry L. Stimson, Taft's secretary of war, to Nicaragua to arrange for peace. By May, Stimson had secured agreement to the suspension of hostilities, the restoration of civil rights, and the recognition of an interim government until elections could be held in 1928.
Relations with Japan were another story. Directly upon learning of the disastrous earthquake and typhoon of 1 September 1923, Coolidge ordered the Asiatic fleet to Yokohama to render assistance. This well-received gesture was followed by further private and public American aid. Japanese-American relations became strained when Congress voted overwhelmingly to exclude Japanese from the quotas established in the new Immigration Act of 1924. Despite the strenuous efforts of Coolidge and Secretary of State Hughes, Congress would not budge on the issue and indeed made very clear in debate its strong anti-Asian sentiment. Relations between the two nations would remain touchy thereafter, although the administration took great care in negotiating other issues with Japan.
Coolidge declined to run for reelection as president in 1928. He was satisfied, if not elated, to be succeeded in the White House by Herbert Hoover. After returning to Northampton in 1929, Coolidge busied himself with literary activities, which resulted in the production of his autobiography, some magazine articles, and, for a year, a syndicated newspaper column. He occasionally engaged in civic and political activities, but he was not a political force, nor did he try to be. He was bothered by minor ailments after he left Washington, and he increasingly complained of ill health in 1932. Nevertheless, his death of coronary thrombosis on 5 January 1933 was unexpected. He was buried in the family plot in Plymouth Notch, Vermont.