Good answers, thank you! But I want more...
Taiwan could've bought German and other surplus submarines after 1945. And Soviet submarines after 1990. And some know how together about it. I mean, Sweden got its first submarine in 1907 and had two dozens of them operational during the cold war. All domestically developed and built. It is hard to start from scratch now, but 30 years ago at least should've been the time to begin this journey.Building submarines is about experience, not about size of shipping industry. You need to start somewhere and take every step forward.
All that was the wrong priority given that they are an island country, of course they needed to give big priority to their submarines! Especially in view of the great success of the US submarines against Japanese shipping during WWII. It should've been a high priority already when the island nation was made independent. I think they've made a huge and unnecessary mistake. Do they somehow have a cultural problem here, like cats love fish but hate water?Taiwan is trying to do just that --- skip the history. They have done this process before --- made their indigenous jet fighter, supersonic antiship missile, their close in RAM equivalents, stealth corvette, and so on.
Just having a quick look at the world map, it seems that one could proclaim a 500 km sea zone from mainland China's coast line for unrestricted submarine warfare, without any foreign ships having any businesses there other than to trade with'em. And what if a Philippine or Australian ship is sunk outside of it? Would they join PRC's war against RoC? If they were always boycotted and now invaded, what do they have to lose? It won't be a Lusitania event.Even if Taiwan has the subs, going to war with them is another problem. How will a Taiwan sub be able to successfully identify a Chinese freighter underwater from let's say a Philippine, Korean, Japanese, Australian, or American flagged ship? The sea traffic around Taiwan are among the densest in the world --- conducting submarine warfare would be like conducting a shootout in a busy New York intersection. Missiles and torpedoes don't differentiate friend or foe--- they only see a target. Someone innocent is going to get into harm's way.
Maybe a modern submarine fleet could be powered by small nuclear power plants. Maybe they could be highly automatized with little crew supply needs. Maybe they could be resupplied from pre-deposited assets at sea. Primitive German submarines stayed at sea for a year or so. As responsible for the military security of Taiwan, being without a submarine fleet would be the biggest imaginable nightmare of all. Everything has to be done to heal that gaping wound.In a protracted war, these submarines will have no base to go home to but their allies. Taiwan's bases would already be blown to bits by missile attacks and even taken over by special forces.