By Mark Trevelyan LONDON (Reuters) -Russian Defence Minister Sergei Shoigu on Wednesday ordered his troops to withdraw from the occupied Ukrainian city of Kherson and take up defensive lines on the opposite bank of the River Dnipro. The announcement marked one of Russia’s most significant retreats and a potential turning point in the war, now nearing the end of its ninth month. In televised comments, General Sergei Surovikin, in overall command of the war, reported to Shoigu that it was no longer possible to keep Kherson city supplied. “Having comprehensively assessed the current situation, it…