Complex sentence: On July 25, the Calgary Highlanders attempted assaults on May-sur-orne and Bourguebus Ridge but found that the assembly area of St. Martin was still occupied with German troops.
Split into simpler sentences: On July 25, the Calgary Highlanders attempted assaults on May-sur-orne and Bourguebus Ridge. Unfortunately, the assembly area of St. Martin was still crawling with German troops.