Complex sentence: Yue Fei ordered his Beiwei (背嵬) and Youyi (游奕) cavalry units to attack the Jurchen using the Guai Zi Ma (拐子马/拐子馬) tactic.
Split into simpler sentences: Yue Fei ordered his Beiwei (背嵬) and Youyi (游奕) cavalry units to attack the Jurchen. During the battle, the Song cavalry employed the Guai Zi Ma (拐子马/拐子馬) tactic.