The U.S. Army awarded a $435 million contract on Friday to build a TNT production plant in western Kentucky that will become the first domestic source for the explosive material in decades, officials said.

Senate Republican leader Mitch McConnell, a key player in securing the funding, said the new facility in his home state is part of a broader retooling of the U.S. defense industrial base that’s needed to deter adversaries abroad. Trinitrotoluene, or TNT, is used in artillery shells, bombs and grenades.

Establishing domestic production of TNT is vital for national defense, the Army said. The current supply chain for the crucial explosive material is entirely reliant on overseas sources, it said.