As his Russian army was outnumbered by far Mikhail Bogdanovich Barclay de Tolly successfully used "delaying operation", defined as an operation in which a force under pressure trades space for time by slowing down the enemy’s momentum and inflicting maximum damage on the enemy without, in principle, becoming decisively engaged, by retreating further eastwards into Russia without giving battle. But the Tsar replaced the unpopular Barclay de Tolly with Kutuzov, who on 18 August took over the army at Tsaryovo-Zaymishche and ordered to prepare for battle. Kutuzov understood that Barclay's decision to retreat had been correct, but the Tsar, the Russian troops and Russia could not accept further retreat. A battle had to occur in order to preserve the morale of the soldiers and the nation. He then ordered not another retreat eastwards but a search for a battle ground eastwards to Gzhatsk (Gagarin) on 30 August, by which time the ratio of French to Russian forces had shrunk from 3:1 to 5:4 thus using Barclay's delaying operation again. The main part of Napoleon's army had entered Russia with 286,000 men but by the time of the battle was reduced mostly through starvation and disease