China has been a good friend to Pakistan. During a visit on April 21 by Chinese President Xi Jinping, the Chinese pledged $46 billion in new infrastructure and energy investment in Pakistan. The two sides are working on another token of China-Pakistan friendship: a purchase by Pakistan of eight Chinese-made submarines capable of carrying anti-ship missiles. According to the official China Daily, the price tag is somewhere between $4 billion and $5 billion. The sale will more than double the size of Pakistan’s submarine fleet and help it keep pace with China and Pakistan’s mutual rival, India, which is expanding its own trove of subs.

The Pakistan purchase extends a submarine race not only on the subcontinent but also in East Asia. Of the world’s 300 submarines that are not part of the U.S. Navy (which has 73), two-thirds are in the Indo-Pacific region, Admiral Samuel Locklear told the U.S. Senate Armed Services Committee on April 16. The region already is “the most militarized part of the world,” he said.

China, asserting its claims to disputed islands in the East and South China Seas, is modernizing its submarine fleet to expand the reach of the People’s Liberation Army. That’s pressuring Japan and South Korea to add to their fleets. Taiwan, after unsuccessfully attempting to buy submarines to modernize a fleet that includes World War II vintage boats, plans to build its own. In Southeast Asia, where governments used to shun subs as too pricey (roughly $500 million to $2 billion each), Indonesia and Vietnam are deploying them.

… The jump in submarine purchases stems in part from the prestige associated with the vessels, which are expensive to buy and complicated to operate. But as their economies have grown, Asian countries that once wouldn’t have purchased even one sub are buying many. “A submarine is a symbol of national power,” says Swee Lean Collin Koh, associate research fellow at the Maritime Security Programme at the S. Rajaratnam School of International Studies in Singapore. A typical military or government official would think, “If my neighbor buys two submarines, then I want to buy two as well,” he says.