북벌
In 228, Zhuge Liang launched his Northern Expeditions against Wei, Ma Su also proposed a plot to remove Sima Yi from command by causing discord within Wei by spreading rumors that Sima Yi intended to rebel and Cao Rui then removed him from command. Many suggested appointing either Wei Yan or Wu Yi () as the vanguard commander, but Zhuge Liang chose the callow Ma Su instead.