In 1957, he was promoted to Brigadier and commander of 99th Gurkha Infantry Brigade Group in Malaya. This was the most demanding and important command in the Army with the task of finally defeating the most formidable remaining terrorists in Johore in Operation Tiger. Walker maintained an excellent relationship with police Special Branch; he took great pains in the development of intelligence, and made frequent use of ambushes. In Malaya, he demonstrated his mastery in ambush skills which he had initially learnt in Waziristan on India's North-West Frontier in 1939 to 1941. He was recognised as a gifted trainer of troops, and had the gift of inspiring confidence and enthusiasm.