Complex sentence: The bombings have been attributed to Islamic extremists and part of a campaign against Westerners and Westernization in Saudi Arabia thought to have been sparked by the stationing of US troops in Saudi Arabia during the 1991 Gulf War with Iraq.
Split into simpler sentences: The bombings have been attributed to Islamic extremists as part of a campaign against Westerners and Westernization in Saudi Arabia. They are thought to have been sparked by the stationing of US troops in Saudi Arabia during the 1991 Gulf War with Iraq.