He converted to Hòa Hảo during World War II, and then quickly rose to prominence as the sect's leading military leader.

[3] Around this time, he converted to Hòa Hảo, founded by Huỳnh Phú Sổ, and devoted his significant energies to advancing through the ranks of the sect.

[4] On 7–9 September 1945,[5][6] a band of 15,000 Hoahaoists armed with hand-to-hand weapons,[7] and aided by the Trotskyists,[6] attacked the Việt Minh garrison at the port city of Cần Thơ, which the Hòa Hảo considered the rightful capital of their domain.

[8] They were led by Soái, his eldest son, Lâm Thành Nguyên, and Sổ's younger brother,[9] but with their antiquated weapons, the Hòa Hảo were defeated and Sổ's men were massacred[5][7] by the Việt Minh-controlled Advanced Guard Youth, who were reportedly aided by a nearby Japanese garrison.

They knew that a direct confrontation with the VNA would be catastrophic, so they burned down to their bases and dispersed their army of 16,000 men into the jungle to operate as guerrillas.