Disaster was completed when the enemy "chest and horns" formation closed, cutting off the road to Rorke's Drift.  
This battle was precipitated by an attack on Sihayo's farmstead.  The attackers marched to the Ngwebeni stream from Ulundi and struck after being discovered by Colonel Durnford's patrol. The defenders, left to guard the camp by Lord Chelmsford, and running low on ammunition, broke when their commander, Henry Pulliene, ordered a retreat to a tighter formation.  Disaster was completed when the enemy "chest and horns" formation closed, cutting off the road to Rorke's Drift.  FTP, name this 1879 battle, the worst British defeat in the Zulu War.
This battle was precipitated by an attack on Sihayo's farmstead.  
Battle of Isandlwana