After becoming world champion by default, Karpov confirmed his worthiness for the title with a string of tournament successes from the mid 70s to the early 80s. He defended his title twice against ex-Soviet Viktor Korchnoi, first in Baguio, the Philippines, in 1978 (6–5 with 21 draws) then in Merano in 1981 (6–2, with 10 draws).