Critically, both Villa's División del Norte and Obregón's forces suffered chronic shortages of munitions. This was due in large part to the demand for ammunition created by the First World War and also to the increasing cost of the ammunition that remained for sale. This lack of ammunition resupply would prove to be a pivotal issue in the Battle of Celaya. Allegedly, some of the ammunition that Villa had purchased before the battle from private vendors from the US was faulty and failed to perform under the conditions of the battle. Whether or not this was deceit on the part of the suppliers is difficult if not impossible to discern. Furthermore, Villa's forces were at a marked disadvantage regarding their artillery. Not only did Obregon's forces possess 15 more artillery pieces than Villa, their scarce European-sourced ammunition was vastly more lethal, reliable and had a further effective range. Before the battle began, Villa was well aware of his force's shortage of ammunition and communicated this in a message to Emiliano Zapata. Additionally, Villa's forces did not attempt to disrupt the resupply of Obregón's forces from the port city of Veracruz.