Subsequently, the limit of Japanese operations in the Indian Ocean was against trade using submarines and armed merchant cruisers. Notably, a submarine group patrolling off East Africa attacked the harbour at Diego-Suarez, Madagascar, while the Allies were capturing the island. Ironically, the Allies were motivated by overblown fears that the Japanese might establish a base there to attack trade. Overall, Japanese attacks on trade enjoyed some success, but after 1942 the presence of major Japanese naval units in the Indian Ocean virtually ceased.