One of America’s most advanced submarines began a port call in the Philippines on Monday.

According to the U.S. embassy in the Philippines, the Los Angeles-class fast-attack submarine USS Chicago (SSN 721) made a port call in Subic Bay, Philippines on Monday. The site was home to one of America’s largest oversea military bases before it was shut down by the Philippines in 1992.

The USS Chicago was the first fast-attack submarine to be built with a vertical launch system, the embassy noted in its press release announcing the visit. The submarine is more than 360 feet long and weighs some 7,000 tons when submerged.

The submarine is capable of supporting numerous different missions, the embassy noted, including intelligence, surveillance, reconnaissance, anti-submarine warfare, anti-surface ship warfare, and strike. It carries a crew of 170 sailors.

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The USS Chicago is forward deployed in Guam, the hub of U.S. Pacific operations. It made an earlier port call in Changi, Singapore back in March of this year.

That the submarine is making a port call to Subic Bay, Philippines is notable. After the Philippines kicked out the Americans in 1992, Manila converted the facility into a trading zone and industrial hub.

It was only last month that the Philippine military officially announced it was re-opening the former naval base for military usage, having leased some of the area from the governmental body that doles out leases for businesses in the zone.

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"It's location is very strategic," Philippine Defense Department spokesman Peter Galvez said at the time, adding: "If we need to deploy to the West Philippine Sea, it (Subic) is already there, we do not deny that. It's a deepwater port."

The Philippine military plans to deploy aircraft and naval vessels at the base.

Last year, the United States and the Philippines signed a new military agreement that would allow the U.S. military to use some of the Philippine bases. That agreement, however, has been held up by a legal challenge in the Philippines. The case is currently being heard by the Supreme Court in the Philippines.

The USS Chicago’s port call to Subic Bay also coincides with a major regional security conference in Asia. On Tuesday, Asian leaders opened up the ASEAN Regional Forum in Kuala Lumpur, Malaysia.

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U.S. Secretary John Kerry will be in Malaysia from Tuesday to Thursday to participate in the regional conference. Following the conclusion of the ASEAN Regional Forum, Kerry will travel to Vietnam to meet with a number of officials from that country, including Deputy Prime Minister and Foreign Minister Pham Binh Minh.

The USS Chicago’s port call to Subic Bay also comes amid growing fears that China will convert the Scarborough Shoal into a military base. Philippine officials told the Wall Street Journal this week that they fear China will reclaim the partially submerged shoal in the near future, and turn it into an artificial island, which they will then militarize.

China seized the Scarborough Shoal from the Philippines in 2012. It is located just 120 miles west of Subic Bay.

Zachary Keck is managing editor of The National Interest. You can find him on Twitter: @ZacharyKeck.

Image: Wikimedia/MC1 Jeffrey Jay Price