What is the importance of The Night of the Long Knives as noted in the biography, Adolf Hitler?

The Night of the Long Knives occurs in July 1934. In the Night of the Long Knives, hundreds of Hitler's opponents are killed both inside the Nazi Party and outside. SA leader Ernst Rohm is killed, and General Schleicher is assassinated by the Gestapo. Many other SA leaders and former political opponents of Hitler, such as Gregor Strasser, are shot without trial.