In early January, the heavylift ship Rolldock Sea entered the Vietnamese port of Cam Ranh Bay towing a submarine. The sub, HQ-182, is a Russian-made Improved Kilo-class boat, one of six ordered by the Vietnamese navy in 2009.

HQ-182, also known as the Hanoi, is Vietnam’s first submarine.

Displacing 4,000 tons underwater, the diesel-powered Kilos have six tubes for launching guided torpedoes or supersonic SS-N-27 “Klub” anti-ship missiles. So quiet that they’re called’ “black holes” by the U.S. Navy, the subs can sit silently off Vietnam’s coast, waiting in intercept and sink any attackers. The six Kilos will be Vietnam’s capital ships.

And Hanoi isn’t the only Asian government buying submarines. Malaysia has also purchased two. Thailand just built a new submarine headquarters—now it just needs the actual subs. South Korea is doubling its undersea fleet, while Japan is growing its sub force by more than a third.

Across Asia and the Pacific, defense budgets are going up and the money is going deep ... very deep. To keep the peace and win at war, the region’s navies are betting on submarines.