Tactical Unit: Comrades in Arms (simplified Chinese: 机动部队 - 同袍; traditional Chinese: 機動部隊 - 同袍) is a 2009 Hong Kong neo-noir action thriller film directed by Law Wing-Cheong. This film is also called "PTU 2", in reference to the first film in the series, PTU, though it is not the second entry in the Tactical Unit series.

"Comrades in Arms" has been featured in the 2009 Hong Kong Film Panorama in Brussels, the 2009 New York Asian Film Festival of New York City, the 2009 Zero em Comportamento festival of Lisbon, and the 2009 Fantasia Festival of Montreal.