JERUSALEM (AP) -- Israeli Defense Minister Ehud Barak abruptly quit politics Monday, potentially robbing Prime Minister Benjamin Netanyahu of a key ally who enabled his hardline government to present a moderate face to the world. Barring another comeback by the mercurial former general, Barak's departure marked an end to a distinguished and tumultuous career that spanned half a century. It began on a communal farm, led to military greatness and business success and a mixed record in politics that was highlighted by failed peacemaking efforts during a brief term as prime minister. Despite polls showing his small centrist Independence Party gaining momentum following the eight-day Israeli offensive in Gaza that he steered, Barak said he would not run again for office in the Jan. 22 elections. "I feel I have exhausted my political activity, which had never been a special object of desire for me," Barak, 70, said in a surprise announcement in Tel Aviv. "There are many ways for me to serve the country and society, not just through politics." Barak will remain as defense minister until a new government is sworn in after the elections. Still, analysts predicted that Israel's most prominent warrior-statesman of his generation had yet to say the last word and was perhaps still angling to keep his job after the election as a special appointment of Netanyahu, who is expected to be re-elected. In recent polls, Barak's party had been struggling to nudge above the electoral threshold needed to get into parliament. "In his position, he did the smartest thing one could do," said Shlomo Avineri, a political science professor at Jerusalem's Hebrew University. "He's not as popular as an electoral candidate as he is a minister of defense. He's not going to say no if he's asked to be the next minister of defense. And he probably will." Over the past four years, Barak gave Netanyahu's governing coalition a well-known face to deal with the international community and Netanyahu himself a loyal and seasoned partner. The two men have been close since the 1970s, when Barak was Netanyahu's commander in the elite Sayeret Matkal commando unit. As prime minister, Netanyahu awarded Barak great influence in decision-making and made him his informal point man to the United States. The Obama administration embraced him as a moderating influence on Netanyahu's hardline policies toward the Arab world and Iran's nuclear program. Barak was scheduled to depart Tuesday for meetings with U.S. officials in Washington. His departure from politics comes at an uncertain time for Israel, with Islamist political parties rising around the Jewish state and a decision looming on whether to strike Iran's nuclear program. The Netanyahu-Barak alliance had its strains over this issue - with the prime minister reportedly objecting to Barak's newly moderate position that Israel should defer to the U.S. in deciding whether to attack Iran should sanctions fail to deter Tehran from attaining a nuclear bomb.