However, during their advance Yakov Zhilinsky, Chief of Staff of the Imperial Russian Army, made a strategic mistake by separating two large Russian armies and urging them to move rapidly over a marginally trafficable terrain in response to the requests of the French for an early offensive. As a result, the armies approached in a poorly coordinated manner, being isolated from each other by terrain obstacles, and before the logistical base could be established, the troops were worn down by a rapid march and had to face fresh German troops.