Complex sentence: The "Shenandoah" destroyed one more prize in the Sea of Okhotsk, north of Japan, then continued to the Aleutians and into the Bering Sea and Arctic Ocean, crossing the Arctic Circle on June 19.
Split into simpler sentences: The "Shenandoah" continued to the Aleutians and into the Bering Seas. She then traveled north, crossing the Arctic Circle on June 19.