The US military has moved its High Mobility Artillery RocketSystem (HIMARS) from Jordan into southern Syria for the first time, positioning it near the US-Coalition training base at At Tanf, three US defense officials confirmed to CNN Tuesday. HIMARS, a truck-mounted system that can fire missiles as far as 300 kilometers, represents a major boost to US combat power near At Tanf, a location that has come under the spotlight following a series of recent coalition strikes against pro-regime forces operating in the area. While this is the first HIMARS deployment to southern Syria, a US official told CNN that this was not the first time HIMARS has been used in the country, with the system being…