Areas in which another state wishes to exert its influence so that no hostile government or ideology can take root there. For example, the U.S. regards Central America as coming within its sphere of influence, which accounts for its attempt during the 1980s to overthrow the communist Sandinista regime in Nicaragua. Before its demise in 1991, the Soviet Union regarded Eastern Europe as its sphere of influence, which is why it felt justified in invading Czechoslovakia in 1968 when that country appeared to be adopting more liberal policies. By and large, each superpower accepted the validity of each other's clearly defined spheres of influence, although there were many areas where spheres of influence were disputed.