Nov. 3, 1983 (UPI) -- President Reagan, declaring U.S. troops successfully accomplished their mission in Grenada, today said the American invasion force will begin withdrawing from the island within days. U.S. Army spokesmen in the Grenadan capital said troops from the 82nd Airborne division were packing their gear and as many as 2,300 soldiers would be flown home in a single wave starting as early as today. Advertisement U.S. Embassy officials in Barbados said the United States was rushing $3.