Arguably the most famous Union Zouave regiments were from New York and Pennsylvania: the 5th New York Volunteer Infantry, "Duryee's Zouaves" (after its first colonel, Abram Duryee), the 114th Pennsylvania Infantry; "Collis's Zouaves" (after their colonel, Charles H. T. Collis); and the 11th New York Volunteer Infantry, the "Fire Zouaves". The 11th New York was initially led by Col. Elmer E. Ellsworth, until his death in 1861. The 11th New York was badly mauled during the First Battle of Bull Run in July 1861 as it acted as the rear guard for the retreating Army of the Potomac. The 5th New York was considered one of the elite units of the Army of the Potomac; it was one of only two volunteer regiments serving with the regular division commanded by George Sykes. At the Second Battle of Bull Run, the 5th New York, along with another Zouave regiment, the 10th New York "National Zouaves", held off the flanking attack of James Longstreet's Corps for ten crucial minutes before it was overrun. The 5th New York thus suffered the highest percentage of casualties in the shortest amount of time of any unit in the Civil War (of 525 men, approximately 120 were killed and 330 were wounded in less than 10 minutes).