Complex sentence: The insurgency took a giant leap forward with the Riyadh Compound Bombings; on May 12, attackers drove three car bombs into residential compounds housing Westerners and others, killing 26 people.
Split into simpler sentences: The insurgency took a giant leap forward with the Riyadh Compound Bombings. On May 12, attackers drove three car bombs into residential compounds housing Westerners and others, killing 26 people.