In the years directly prior to Fidel Castro’s retirement, Cuba was undergoing immense changes. These changes were brought on in part by the 1991 collapse of the Soviet Union, which had been Cuba’s chief ally and trade partner. Castro sought to offset the ensuing market decline by allowing the implementation of a limited number of economically liberal reforms. Raúl Castro—Fidel’s younger brother and successor—continued to gradually adopt free-market policies. The island nation’s newfound economic liberalism, combined with a rollback in some of its more repressive policies, led to improved U.S.-Cuban relations. In 2014 U.S. Pres. Barack Obama and Raúl Castro agreed to reopen diplomatic relations and halt the trade embargo, both of which had been in effect for over five decades. In 2017 U.S. Pres. Donald Trump restored some of the commercial and diplomatic restrictions that had been lifted under Obama.