Complex sentence: Some East Asian historians believe this technological breakthrough alongside the turtle ship in the mid- 16th century had a distinctive effect during the Imjin War; however, sources on both the turtle ship and hwacha are too scarce to really say much about this.
Split into simpler sentences: Some East Asian historians believe this technological breakthrough alongside the turtle ship in the mid- 16th century had a distinctive effect during the Imjin wars. But sources on both the turtle ship and hwacha are too scarce to really say much about this.