It was a risky operation, beginning with a movement of Cuban troops in divisional strength west of the Cunene River, which had the potential to expand into an invasion of South West Africa. On 9 March, Castro sent the Cuban forces massed at Lobito, which had grown to about 40,000 men, southwards. He likened their movement to "a boxer who with his left hand blocks the blow Cuito Cuanavale and with his right – strikes the west". "That way," Castro recounted on another occasion, "while the South African troops were being bled slowly dry in Cuito Cuanavale, down in the southwest...40,000 Cuban soldiers...backed by about 600 tanks, hundreds of artillery pieces, 1,000 anti-aircraft weapons, and the daring MiG-23 units that took over the skies, advanced towards the Namibian border, ready to sweep away the South African forces".