Complex sentence: After that, starting with February 1919, enough Romanian troops were present in Bessarabia to thwart most attack attempts of the Bolsheviks who at that time had to deal with the advancing Armed Forces of South Russia led by Anton Denikin.
Split into simpler sentences: After that, starting February 1919, enough Romanian troops were present in Bessarabia to thwart most attack attempts. At that time, the Bolsheviks had to deal with the advancing Armed Forces of South Russia led by Anton Denikin.