Complex sentence: In the 1970s, a brand of revisionist, non-traditional samurai film rose to some popularity in Japan; the subgenre became known as "chambara", an onomatopoeia describing the clash of swords.
Split into simpler sentences: In the 1970s, a revisionist, non-traditional style of samurai film achieved some popularity in Japan. It became known as "chambara", an onomatopoeia describing the clash of swords.