First encountered on 23 June 1941,[24] the T-34 outclassed the existing Panzer III and IV.[25] At the insistence of General Heinz Guderian, a special Panzerkommision was dispatched to the Eastern Front to assess the T-34.[26] Among the features of the Soviet tank considered most significant were the sloping armor, which gave much improved shot deflection and also increased the effective armor thickness against penetration, the wide track, which improved mobility over soft ground, and the 76.2 mm gun, which had good armor penetration and fired an effective high-explosive round.