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In page Paul von Hindenburg:

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In the spring of 1916, the Central Powers experienced a military catastrophe in the East that left Germany bearing much of the war effort until the end of hostilities. On 4 June, the Russian Army began a massive offensive along 480 km (300 mi) of the southwestern front in present-day western Ukraine. In the ensuing onslaught, four armies commanded by General Aleksei Brusilov overwhelmed entrenchments that the Austro-Hungarians long regarded as impregnable.[1] Probing assault troops located three weak spots which then were struck in force. In nine days they captured more than 200,000 men and 200 guns and pushed into the open country.[citation needed]