One of the most important munitions of the Ukraine war comes from a historic factory in this city built by coal barons, where tons of steel rods are brought in by train to be forged into the artillery shells Kyiv can’t get enough of — and that the U.S. can’t produce fast enough. The Scranton Army Ammunition Plant is at the vanguard of a multibillion-dollar Pentagon plan to modernize and accelerate its production of ammunition and equipment not only to support Ukraine, but to be ready for a potential conflict with China. But it is one of just two sites in the U.S. that make the steel bodies for the critical 155 mm howitzer rounds that the U.S. is rushing to Ukraine to help in its grinding fight to repel the Russian invasion in the largest-scale war in Europe since World War II. The invasion of Ukraine revealed that the U.S. stockpile of 155 mm shells and those of European allies were unprepared to support a major and ongoing conventional land war, sending them scrambling to bolster production. The dwindling supply has alarmed U.S. military planners, and the Army now plans to spend billions on munitions plants around the country in what it calls its most significant transformation in 40 years. It may not be easy to adapt: practically every square foot of the Scranton plant’s red brick factory buildings — first constructed more than a century ago as a locomotive repair depot — is in use as the Army clears space, expands production to private factories and assembles new supply chains. There are some things that Army and plant officials in Scranton won’t reveal, including where they get the steel for the shells and exactly how many more rounds this factory can produce. “That’s what Russia wants to know,” said Justine Barati of the U.S. Army’s Joint Munitions Command. So far, the U.S. has provided more than $35 billion in weapons and equipment to Ukraine. The 155 mm shell is one of the most often-requested and supplied items, which also include air.