Complex sentence: Instead of heading for France, these units were trained and re-outfitted in England with Russian guns and then sent to North Russia, where they arrived in Arkhangelsk on September 4,1918 and were placed under British command.
Split into simpler sentences: Instead of heading for France, these units were trained and re-outfitted in England with Russian guns and then sent to North Russia. They arrived in Arkhangelsk on September 4,1918, coming under British command.