Showing exactly how dangerous he remained even while semi incapacitated (he was recovering from a wound by this time), how capable he remained in regards to rebuilding his forces, and how ineffective the US mission had become, Pancho Villa raided Ciudad Chihuahua on this day with about 2,000 to 4,000 men, a considerable increase in the number he'd had only a few short weeks ago. Indeed, at the time of his raid on Columbus, New Mexico, he was down to a few hundred and had been down to as few as 400 men just a few weeks prior to this date. His main target was the prison, where many of the men freed were former soldiers of his. The raid is remarkable in that it was conducted in the face of the US presence while against Carranza's forces.
Villa leading his forces prior to his 1915 defeat at Celaya, from the post noting the raid on Columbus, New Mexico, in real time.
The raid was a success in spite of a Constitutionalist force being in town. Villistas occupied the city during the night and withdrew in the early morning hours. Recent efforts by the U.S. Army to corner Villa had resulted in some engagements and sightings, but no success. And he remained capable of taking Carranza.
Pershing had recently gone on record as arguing that only the occupation of the entire state of Chihuahua would be effective in the campaign against Villa, and he'd urged the same. This raid seemed to reinforce his view, but fairly clearly the occupation of the entire state would risk war with Carranza, no matter how ineffectual he was, and therefore there was no realistic chance that Wilson would authorize such an action. Villa, therefore, in desperate straits just a few weeks prior, seemed, in some ways, to have effectively called the American bluff.