US submarines are getting new long-range ship-killer missiles as China's large navy keeps getting bigger

• The US Navy plans to arm submarines with a new version of the Tomahawk missile next fall.
• The Maritime Strike version has a new guidance system to engage mobile targets at sea.
• It's the latest US anti-ship effort as rival China continues to build up its already large navy.

Starting next fall, US submarines will be equipped with a new version of a widely used and powerful cruise missile. 

The move to arm boats with Maritime Strike Tomahawk (MST) missile, a stand-off anti-ship capability with a longer range than torpedoes,  comes as rival China, which the Pentagon calls America's "pacing challenge," continues to build up its already large navy and as tensions persist between China, its neighbors, and the US.

On Tuesday, the US Navy announced plans to field the ship-killer versions of the Tomahawk Land Attack Cruise Missile after October 1, 2024, Capt. Jon Hersey, the program manager for the Tomahawk Weapons System program office, said in a statement reported by Bloomberg.

He added that this version of the long-range cruise missile, designed by RTX Corporation, has been modified with a new guidance system "to engage a mobile target at sea," such as a warship. Initial versions of the MST were tested last year. 

With the new addition, US submarines will have a deadly Tomahawk missile able to target ships possibly as far out as 1,000 miles, which will help the Navy deter against growing challenges from China, which boasts the largest Navy in the world. In its latest report on China's military power, the Pentagon said China had 370 ships and submarines, almost 100 more than the US Navy. The US, however, is believed to still maintain advantages in warship quality, though the gap is narrowing.

Many of the ships being fielded by China are new, more advanced ships. Some were involved in the massive display of naval power in August 2022 after former US House of Representatives Speaker Nancy Pelosi's visit to Taiwan stirred tensions with Beijing.

Back in March, Gen. Kenneth Wilsbach, the commander of the US Pacific Air Forces, warned that Chinese ships would be the first target US forces would have to deal with if China were to invade Taiwan, saying that "those ships can put up an anti-access/area-denial engagement zone, which comes from their surface-to-air missiles that they can shoot from the ships. So in order for us to get past those, we've got to sink the ships."

While that is something the Air Force is looking at, along with the Army and Marines as well, that is still a key Navy mission. The MST could be a new, threatening way to do that, giving US naval forces a better chance at checking China's might at sea in the event that a conflict arose.

But China's bolstered rocket force, too, has the US military concerned, as China doubled its inventory of a number of missiles in the past year. It has so much of one particular missile, nicknamed the "carrier killer," that the weapon could easily threaten a variety of ships.