Complex sentence: The "D" model was later deemed an obsolescent design, and the two "E" models were used to develop B-17 air combat counter-tactics; they were also used as enemy aircraft in several Japanese propaganda films.
Split into simpler sentences: The "D" model was later deemed an obsolescent design. The two "E" models were used to develop B-17 air combat counter-tactics; they were also used as enemy aircraft in several Japanese propaganda films.