Members of the People's Liberation Army Marine Corps during training in Zhanjiang, Guangdong province, July 20, 2017.REUTERS/Stringer China's ability to invade Taiwan has gotten renewed attention amid heightened tensions in recent weeks. China's military has devoted much effort to improving its ability to conduct such a risky and costly operation. A key part of that operation would be China's Marine Corps, which has more than doubled in size since 2017. China's Marines would be key in a Taiwan War: Tensions between China, the US, and Taiwan have risen following a visit by US House Speaker Nancy Pelosi to the self-governing island.