Since the “Pivot to the Pacific” and Russia’s increasing aggressiveness in Europe, the Army has been reconsidering its roles. One possibility is to turn the concept of Anti-Access/Area Denial (A2AD) against the Chinese and fortify the “First Island Chain” with Army provided Anti-Ship and Anti-Air Systems. It has been proposed that the Army use mobile Anti-Ship Cruise Missile (ASCM) launchers for this purpose, particularly in the vacinity of vital Straits providing access to the South China Sea and East China Sea, but it looks like they are going a different way.
BreakingDefense reports that the Army is looking at how they might use existing systems to provide these capabilities. If the Army develops these capabilities, and they are still based in the US, it might be possible to develop relationships that would allow the Coast Guard to call on them, if there is a threat to the US Coast. In US law, Coastal Defense is still an Army mission. The capability might be particularly useful in Alaska where available forces are at a minimum and the Coast Guard constitutes a substantial part of the military/naval presence and transportation capability.
The BreakingDefense post talks about the use of guided projectiles for the 155mm howitzer and Multiple Rocket Launcher System (MRLS) and use of the 30mm gun with air burst ammunition to provide a basic anti-aircraft (AAW) capability. Since the Coast Guard is or will be using the Mk38 mod2/3 on a the Webber class and the Offshore Patrol Cutter and this mount can also accept the 30mm gun, it might also provide the cutters with additional AAW capability.
Shipboard use of the 155mm Howitzer and the Multiple Rocket Launcher System has been considered many times. They would provide a great Naval Surface Fire Support (NSFS) capability, but no naval systems have been actually developed. The additional capability to use these systems in an anti-ship mode might provide the motivation necessary to actually field one of these systems.