Complex sentence: In 1925, Minh was introduced to Hồ by Lâm Đức Thụ, also a leader of Thanh Niên, but later exposed as an informer to French police.
Split into simpler sentences: In 1925, Minh was introduced to Hồ by Thụ. Thụ was at this time active in Thanh Niên, although he was later exposed as an informer to French police.