Before giving Ukraine a number of advanced rocket systems that have allowed its forces to level the playing field, striking Russian units from far beyond enemy lines, the Pentagon quietly modified the system’s launchers so they were unable to fire long-range missiles, U.S. officials told The Wall Street Journal. The newspaper reported Monday that the Biden administration believed this was necessary to avoid the risk of escalating the conflict. Since June, the U.S. has given Kyiv around 20 advanced HIMARS, or M142 High Mobility Artillery Rocket Systems, along with rockets with a 50-mile range that have allowed Ukrainian soldiers to target Russian command posts and ammunition deposits. But an unmodified HIMARS launcher has the capability to fire rockets with ranges of nearly 200 miles—long-range weapons that the U.S. has not provided but that Kyiv could potentially secure elsewhere, officials said. The Pentagon declined to comment on the exact nature of the modifications, which officials said involved adjustments to both hardware and software.