The next day, July 18, Tyler's division was ordered to probe the Confederate position on the other side of Bull Run. Richardson's brigade led the reconnaissance-in-force known as the Battle of Blackburn's Ford during which the 1st Massachusetts acted as the leading regiment of the brigade by Col. Cowdin's request. The 1st Massachusetts went into their first battle wearing their gray Massachusetts militia uniforms (the typical color for many state militia units). This caused considerable confusion for both Confederate and Union units that encountered the regiment. After they crossed Bull Run at Blackburn's Ford, three companies of the 1st Massachusetts were ordered forward as skirmishers to probe the Confederate position. These two companies took the brunt of the unit's casualties during the engagement, although the entire regiment was exposed to heavy fire. The 1st Massachusetts found that the Confederates were present in force on the other side of Blackburn's Ford and had a strong position. Tyler ordered a complete withdrawal. Any attempt to flank the Confederate position by Blackburn's Ford was thereafter lost. The 1st Massachusetts suffered casualties of 13 killed in action and 20 wounded and missing.