Complex sentence: Denikin hoped to hold the crossings of the Don, rest, and reform his troops, but the White Army was not able to hold the Don area and at the end of February 1920, started a retreat across Kuban towards Novorossiysk.
Split into simpler sentences: Denikin hoped to hold the crossings of the Don, rest and reform his troops. But the White Army was not able to hold the Don area, and at the end of February 1920 started a retreat across Kuban towards Novorossiysk.