"Night of the Long Knives"
The Blood Purge is also known as the Night of the Long Knives. The night was a brutal and swift purge of the Nazi party, particularly focussing on the removal of any threats to Hitler's personal power from within the SA.
On the night of 30th June 1934 Hitler ordered the SS and the gestapo to round up and imprison or kill the leaders of the SA, the nazi parties oldest and most powerful group which had acted as the leaderships bodyguards since the parties inception and throughout it's rise to power.
The Purge was neccessary to prevent the party suffering from internal divisions. the leadership of the SA had a different political agenda to that of the party hierarchy. Ernst Rohm, the head of the SA was an advocate of absorbing the armed forces into the SA, he was more radical in many respects than Hitler and in doing so had created rifts between hitler and many of the parties supporters.
Conservative follwers of the party were concerned by the rhetoric and actions of the SA, who were oposed to a return of the 'Old order'. The generals were clearly going to be upet by rohm's insistence on the army being absorbed into the SA and other members of the party leadership were becoming inceasingly suspicious of the power and influence of Rohm and other senior figures within the organisation.
The solution was simple. erradicate the problem through use of force, these men were a threat to the stability of the party and posed a direct threat to Hitler's position as leader of the Party and the country.
http://www.schoolshistory.org.uk/weimarandnazigermany/bloodpurge.htm