Bearing in mind the lack of hard evidence on the question and the substantial underestimation of last fall. we conclude that no one in official U.S. sources can tell. with any real degree of confidence. how many Russians are now in Cuba. We feel that the official 17.500 estimate is perhaps a minimum figure. Other sourcesprimarily refugee and exile groupsestimate that as many as 40.000 Soviets are now in Cuba. In any event. it is conceded that the combined Soviet and Cuban forces now in the island are quite powerful defensively and could offer severe opposition to any attack. These Communist forces have an extensive and quite numerous array of modern weapons. including some of the latest types in the Soviet arsenal.