Complex sentence: The figure does not include the smaller Second Strategic Echelon, which as of 22 June 1941 was in the process of moving toward the frontier; according to the Soviet strategic plan; it was scheduled to be in position reinforcing the First Strategic Echelon by early July.
Split into simpler sentences: The figure does not include the smaller Second Strategic Echelon which, as of 22 June 1941, was in the process of moving towards the frontier, according to the Soviet strategic plan. It was scheduled to be in position reinforcing the First Strategic Echelon by early July.