Original: After composing a second string quartet ( 1946 ) , his strongest achievement in the world of chamber music , Walton dedicated the considerable period of seven years to his three-act tragic opera , Troilus and Cressida ( 1947-1954 ) .
Simplified: After composing a second string quartet ( 1946 ) Walton spent most of the next seven years writing his opera , Troilus and Cressida ( 1947-1954 ) .