Russia has been thwarting US-made mobile rocket systems in Ukraine more frequently in recent months, using electronic jammers to throw off its GPS guided targeting system to cause rockets to miss their targets, multiple people briefed on the matter told CNN.Ukrainian military officials, with the US’ help, have had to come up with a variety of different workarounds as it continues to use the High Mobility Artillery Rocket System (HIMARS) which has been perhaps the most revered and feared piece of weaponry in Ukraine’s fight.The medium-range rocket systems were hailed as a game changer in the conflict and have played...