Complex sentence: Iran began to rely on its new Revolutionary Guard's navy, which used Boghammar speedboats: fitted with rocket launchers, RPGs, and heavy machine guns, these speedboats would launch surprise attacks against tankers and cause substantial damage.
Split into simpler sentences: Iran began to rely on its new Revolutionary Guard's navy, which used Boghammar speedboats fitted with rocket launchers and heavy machine guns. These speedboats would launch surprise attacks against tankers and cause substantial damage.