"I am instructed by First Chief Carranza, to inform you, that any movement of American troops from their present lines to the south, east or west will be considered as an overt act and will be the signal for hostilities."
To this message General Pershing replied, under date of June 18, 1916:
"I have not received any orders to remain stationary or withdraw. If I see fit to send troops in pursuit of bandits to the south, east or west, in keeping with the object of this expedition, I shall do so. If any attack is made on any part of my forces when performing such duties, the entire military strength of the expedition will be used against the attacking forces."
A short time after these threats were exchanged, a force of several hundred Mexican soldiers, armed with machine guns, attacked a small detachment of American cavalry killing several of their number, including two fine young officers. This killing of American soldiers, considered in the light of all the circumstances under which it occurred and the overwhelming force that attacked our men, was virtually assassination by lying in wait, but it was not succeeded by the "serious consequences" mentioned by our Secretary of State, nor was "the entire military strength of the expedition" used against the attacking forces, as
