Complex sentence: On 23 August it captured one of the main objectives of the offensive, but only in part, taking the southern half of Zubtsov, and thereafter its units reached the river Vazuza and carved out a shallow bridgehead on the western bank.
Split into simpler sentences: On 23 August it captured one of the main objectives of the offensive, taking the southern half of Zubtsov. Then, its units reached the river Vazuza and carved out a shallow bridgehead on the western bank.