Complex sentence: From the 1250s the fortunes of the Knights Hospitaller took a turn for the worse and in 1271 Krak des Chevaliers was captured by the Mamluk Sultan Baibars.
Split into simpler sentences: From the 1250s the fortunes of the Knights Hospitaller took a turn for the worse. In 1271 Krak des Chevaliers was captured by the Mamluk Sultan Baibars.