Tảng believed that Thục "undoubtedly considered that Thảo's Catholic and family loyalties were stronger and more durable than his youthful enthusiasm for revolution". He felt that Thảo had tricked Thục into believing that he was no longer a communist, and that his inside knowledge would be useful to the Ngô family. Thảo started by training the Civil Guard. As a result of his family's Catholic connections, Thảo rose steadily in the ARVN, since Diệm's regime had always promoted officers primarily on religious preference and loyalty. Nhu sent him to Malaysia to study counterinsurgency techniques, and upon his return, Thảo became a vital part of Nhu's efforts to purge the army of disloyal officers. As Thảo kept a close watch on those who commanded troops, lest they use their personnel in a coup, the leading officers were keen to maintain a good relationship with him, which increased his effectiveness as a spy. Thảo rose even further when the troops he commanded helped put down the November 1960 coup attempt against Diệm. Thảo assisted Khánh and Trần Thiện Khiêm to put down the revolt. All three were promoted, with the latter pair gaining the leadership of the ARVN and of the combined forces, respectively. This cemented the trio's close ties.