Complex sentence: Armed primarily with machetes and 19th-century rifles, they attempted to besiege the Marines, but were easily repulsed with the help of one of the first dive bombing attacks in history, conducted by five Marine de Havilland biplanes.
Split into simpler sentences: Armed primarily with machetes and 19th-century rifles, they attempted to besiege the Marines. However, they were repulsed with the help of one of the first dive bombing attacks in history, conducted by five Marine de Havilland biplanes.