President Joe Biden provided details on the latest package—which includes four High Mobility Artillery Rocket Systems, known as HIMARS, 200 mine resistant vehicles, hundreds of thousands of rounds of artillery and mortar ammunition—in a call with Ukrainian President Volodymyr Zelenskyy.The systems—which will bring the total number of HIMARS sent to Ukraine to 20— have become a key tool in Ukraine’s ability to strike bridges that Russia has used to supply its troops, enabling Ukrainian forces to make inroads in Russia-controlled regions.The U.S. in recent weeks also provided funding through a separate program — the Ukraine Security Assistance Initiative — so another 18 HIMARS can be purchased through longer-term contracts.USAI funds are being used as part of the effort by the U.S. and Western allies to ensure Ukraine’s forces are trained and equipped to defend their country in the years to come.Ukraine has pressed its counteroffensive in the Kherson region since the summer, relentlessly pummeling Russian supply lines and making inroads into Russian-held areas west of the Dnieper River."