The submarines will use a combat system by US defence company Lockheed Martin Corp and carry US-made torpedoes.
Admiral Huang Shu-kuang, Ms Tsai's security adviser, described the submarines as a "strategic deterrent" that could also help maintain the island's "lifeline" to the Pacific by keeping ports along Taiwan's eastern coast open.
China openly ridiculed Taiwanese hopes for what the submarines could do to defend the island.
“No matter how many weapons the Democratic Progressive Party buys, it will not obstruct the greater trend of reunification with the motherland,” said Senior Colonel Wu Qian, a spokesperson in China's Ministry of National Defense.
And yet, under the KMT government relations were normalizing. In the past, mainland China had extremely positive rhetoric towards Taiwan (and Taiwan towards mainland China). Even today, trade grows and cultural coupling grows.
Frankly, claiming that China violates Taiwan's airspace shows a gross misunderstanding of international aviation law. American FONOPs in the area since 2016 have broken the status quo that the Chinese and Taiwanese governments were using to split the strait: if the strait is international waters outside of the 12km limit, then the air above it is international airspace by definition.
Oddly enough, that timeline also coincides with Taiwan's government flipping from KMT rule to DPP rule.