China's arms buildup over the last two decades would give it the power to invade Taiwan by 2020 even if allies came to the island's aid, a military report said Tuesday. The mainland's annual military spending has grown on average by double-digit rates over the past 20 years or so, according to Taiwan's 2013 National Defense Report. Aside from military might, it said, China's capacity for weapons research and manufacturing had greatly increased, "which has boosted its military deterrent and posed a grave threat to Taiwan". Among the new weapons China had acquired, both locally produced and purchased from Russia, were nuclear-powered and conventional submarines, strategic bombers, stealth fighters, early warning aircraft and ballistic and air defense missiles, it said. "With the continued arms buildup, the Chinese communists will be able to take Taiwan by force before the end of 2020," it said.