Complex sentence: The apogee of this upsurge was the anti-Ottoman Chiprovtsi Uprising of 1688, after the suppression of which the town's entire population either fled to Habsburg-ruled lands or was killed or enslaved by the Ottomans.
Split into simpler sentences: The apogee of this upsurge was the anti-Ottoman Chiprovtsi Uprising of 1688. After the suppression of the uprising, some of the town's population fled to Habsburg-ruled lands; those unable to flee were killed or enslaved by the Ottomans.