During heavy rains , it was much more difficult to track insurgents by air , negating Portugal 's air superiority , and Portuguese troops and vehicles found movement during rain storms difficult . In contrast , the insurgent troops , with lighter equipment , was able to flee into the bush ( the mato ) amongst an ethnically similar populace into which they could melt away . Furthermore , the FRELIMO forces was able to forage food from the surroundings and local villages , and was thus not hampered by long supply lines .