Complex sentence: On 18 July, the panzer groups came to within of closing the gap but the trap did not snap shut until 5 August, when upwards of 300,000 Red Army soldiers had been captured and 3,205 Soviet tanks were destroyed.
Split into simpler sentences: On 18 July, the Panzer Groups came to within of closing the gap, but the trap did not snap shut until early August. When the Panzer Groups finally closed the gap on 5 August, upwards of 300,000 Red Army soldiers had been captured and 3,205 Soviet tanks were destroyed.