Retired General John Shalikashvili, a former Chairman of the Joint Chiefs of Staff during the 1990s, has died, CNN reported on Saturday, according to Reuters. A Pentagon spokesman would neither confirm nor deny his death and his cause of death was not immediately reported. The Polish-born Shalikashvili, who was 75, came to the United States as a teenager and rose to become the highest-ranking officer in the U.S. military. He served as Chairman of the Joint Chiefs of Staff under President Bill Clinton from 1993 to 1997, heading the U.S. role in NATO air strikes on Bosnian Serb military targets in 1995. Shalikashvili succeeded Gen. Colin Powell as chairman of the joint chiefs. Born in Warsaw in 1936 shortly before World War Two, he fled to Germany in a cattle car in 1944 ahead of the Soviet advance. After retiring from the military, he served as a visiting professor at Stanford and Harvard Universities and publicly endorsed Democratic Sen. John Kerry of Massachusetts in Kerry's losing 2004 presidential campaign. Shalikashvili, who also served as a director of the Boeing Co. , survived a massive stroke in 2004 at his home near Fort Lewis, Washington, next to Tacoma.