Yitzhak Shamir served four terms as prime minister in the 1980s and early '90s. His unyielding pro-settlement views and tough stance toward the Palestinians often exasperated U.S. policymakers.JERUSALEM — Yitzhak Shamir, the onetime underground Jewish fighter and long-serving Israeli prime minister whose unyielding belief in the right of Jews to all of the biblical Land of Israel often exasperated U.S.