In January, the U.S. Naval Institute published a proposal written by a team of defense experts that called on the United States to devise a method of arming merchant container ships with missile defense platforms and even offensive weapons. The concept was meant to relieve basic missile defense operations from the U.S. Navy‘s fleet of Arleigh Burke-class destroyers, freeing them up for more complex or dangerous operations elsewhere.

The concept, while economically sound, seems unlikely to ever come to fruition within the U.S. military unless a large-scale conflict were to arise, but now it seems China has a growing interest in fielding “missile merchant” vessels all its own.

The idea behind using containers to house long-range missiles is simple. Cargo and container ships are seen as non-combatant vessels, and while the U.S. Navy‘s proposal would have included changing the ship designations on container ships purchased to serve as defensive platforms, China’s plan doesn’t include the same level of transparency. By hiding weapons systems in containers that are identical to those found on civilian vessels, China can engage enemy assets from concealed positions that would not otherwise be deemed a threat.

Representing a far more pressing threat, the long-range cruise missiles housed within these shipping containers are reportedly a land attack variant of the YJ-18C anti-ship missile. That suggests this platform is intended not as a defensive weapon, but rather as an offensive one meant to be snuck into foreign ports to be used for surprise attacks against land-based targets.

“It fits with China’s penchant for seeking asymmetric advantages against its enemies,” said Rick Fisher, a senior fellow at the International Assessment and Strategy Center that specializes in studying the Chinese military. He went on to explain these platforms are also in keeping with China’s penchant for deniable weapons systems that are difficult to identify or track.

“Containerized missiles give China, Russia, and its rogue state partners new options for directly or indirectly attacking the United States and its allies,” Fisher said. “Shipping container missile launchers can be smuggled through ports or via highway ports of entry and stored for years in a climate-controlled building within range of U.S. military bases, and taken out when needed for military operations.”

Because of the large volume of Chinese-flagged container ships sailing into U.S. ports at any given time, it would be all but impossible to prevent these weapons systems from finding their way into American ports. These ports dot our nation’s East and West Coasts and are often well within striking distance of nearby military installations. Experts estimate as many as four of these missiles could be housed in a single shipping container, allowing for a near-simultaneous attack on four separate targets at ranges of up to 1,000 miles.

“If this capability is confirmed, it will require a completely new screening regimen for all PRC-flagged commercial ships bound for U.S. ports,” Retired Navy Capt. Jim Fanell, former Pacific Fleet intelligence chief, told the press.