Xi can build largest military, but can it hide force needed to take Taiwan?

China could face an extraordinary military and political gamble if Xi Jinping orders an invasion of Taiwan. Roughly 100 miles of sea, limited landing beaches and a massive military buildup that could be difficult to conceal would complicate Beijing's plans. Even a blockade could disrupt international shipping while inflicting economic pain on China itself. And capturing Taiwan may only begin another challenge if resistance continues after major territory falls. With Xi needing confidence in a rapid victory before taking such a risk, what would finally convince Beijing that the moment to attack has arrived?