Allied support could begin with intelligence and submarines

A large amphibious mobilization would create observable warning signs as commercial ships left normal work, gathered in port, and received hurried maintenance. If allies become involved, intelligence sharing is the most likely first contribution in this scenario. Submarines offer a potentially deniable way to attack shipping because losses could initially be attributed to Taiwanese boats, especially when they use the same weapons, although that deniability is uncertain. Taiwan's distance from suppliers remains a difficulty, but its ports offer several approaches that nearby island chains could help secure. Continued resistance would allow more outside forces to arrive. Allied submarines and carrier groups could then make it harder for Chinese forces to receive supplies and sustain the invasion.