LitCharts assigns a color and icon to each theme in Richard III, which you can use to track the themes throughout the work.
Power
The Throne and the State
Language
Women
Time
Summary
Analysis
At another part of the field, Norfolk enters with his forces and Catesby calls to him for help. He says that Richard's horse has been killed but that Richard fights madly on by foot, determined to kill Richmond. Richard enters shouting, "my kingdom for a horse!" Catesby tries to assist Richard, who seethes that he has killed five Richmonds so far but not the right Richmond. Richard runs off. Norfolk and Catesby exit.
The words Richard screamed as he woke from his nightmare ("another horse") turn out to have been prophetic. Horseless, senseless with rage, unable to find Richmond, Richard is profoundly disempowered on the field.