https://twitter.com/ArmchairW/status/1780850610864267756

The US Army cancelled the XM1299 Extended Range Cannon Artillery (ERCA) system last month. ... The only way I can describe it at this point is total organizational failure. We're now on our third failed program to replace the M109 155mm self-propelled howitzer, and as usual for the US Army the interim solution - the M109A7, basically dropping the existing M109A6 Paladin turret onto a Bradley chassis - is going to end up as the permanent fix.

Let's walk through the history of this generational procurement failure. The M109 has been the US Army's 155mm self-propelled howitzer since before Vietnam, with the original short-barreled version (rather resembling a Russian 2S3) upgraded to sport what was then a very modern 39-caliber* cannon shortly after that war with the M109A1. Further upgrades followed, culminating in the M109A6, a modern weapon of the late Cold War era that was in some way groundbreaking but in some other ways quite dated. It had a lot of new electronics... and a manually-loaded cannon from the 1970s. When the Paladin entered service in the early 1990s the then-Soviet Union had already introduced the 2S19 in 1989 (featuring an autoloading 47-caliber 152mm cannon), and the Germans were hard at work on the PzH 2000 (with a semi-autoloading 52-caliber 155mm cannon). Both of these competing systems could fire three times the rounds of the Paladin at considerably longer ranges.

It wouldn't be an issue because the Army was working on a replacement already - the XM2001 Crusader, a thoroughly modern self-propelled gun with a 52-caliber 155mm cannon and an automatic transloader vehicle. It was the ultimate cannon to defend the Fulda Gap against the Red Tide... which was problematic at the time because that threat didn't exist any more and doubly so after 9/11. So like many Cold War legacy programs it was cancelled by Donald Rumsfeld during his apocalyptic tenure as George W. Bush's Secretary of Defense.

Not to worry, the Army had a backup plan! Enter Future Combat Systems, a program that happened because the Army brass saw the Air Force make the F-35 too big to fail and thought that was a good procurement model. The XM1203 Non-Line of Sight Cannon (NLOS-C), developed as one of the FCS "family" of tracked combat vehicles, sporting a lightweight 39-caliber 155mm cannon with a high-speed autoloader and minimal crew requirements. It would have been the ideal cannon for the lightweight expeditionary Army of the post-Cold War era... and then Iraq happened. The bad part of Iraq where we were losing a hundred guys killed every month with no end in sight. After the Republicans were routed in the 2006 elections and Rumsfeld shown the door his successor, Robert Gates, axed the entire program as yet another Rumsfeld-era boondoggle with no value to win the War on Terror.

This left the Army's fleet of increasingly-worn out M109A6s soldiering on into the 2010s, and replacement vehicles were needed. Enter the M109A7 - basically a program to drop the existing M109A6 turret onto a suitably adapted Bradley chassis to ease maintenance and recapitalize the fleet. The M109A7 didn't offer any actual new capability, but it would keep the Field Artillery in business until a new cannon could be brought into service, because it was now the late 2010s and most serious armies on the planet had moved on to autoloading long-barrel systems.

Enter ERCA, the US Army's plan to leapfrog the competition with a fantastically long 58-caliber 155mm cannon... mounted on the same Bradley-derived chassis of the M109A7. If you take a short survey of modern tracked, armored, long-barrel SPGs - 2S19, 2S35, K9, PzH 2000, etc. - you'll notice that they're all quite heavy, with most of them built on a tank chassis or a specialized heavy artillery chassis. That capability isn't free. The Army was trying to stuff an even longer autoloading cannon onto an IFV chassis, and ran into easily-predictable issues with weight and then - once they cut capability to fix it - into equally predictable issues with bore wear given the extreme ranges they were trying to drive this cannon to (70+ kilometers for a gun about 10% longer than cannons maxxing out at half that). So that program got cancelled last month for what were basically technical feasibility issues.

In any event the US Army's current plan seems to be to go to war with the M109A7 and, if the performance of similar 39-caliber systems in Ukraine is any indication, lose the counter-battery fight and get a lot of artillerymen killed manning obsolescent guns.