CHASIV YAR, Ukraine, March 3 (Reuters) - Russian artillery pounded the last routes out of Bakhmut on Friday, aiming to complete the encirclement of the besieged Ukrainian city and bring Moscow closer to its first major victory in half a year after the bloodiest battle of the war. The head of Russia's Wagner private army said the city, which has been blasted to ruins in Russia's more than seven month onslaught, was almost completely surrounded with only one road still open for Ukraine's troops. Ukraine and its allies say the invasion was an unprovoked war of conquest