The medical corps suffered at all times from the low quality of its personnel and from its defective equipment; and the accommodations for surgeons in a campaign were so poor that many found pretexts for remaining behind when their corps took the field. The commissaries had peculiar difficulties to meet. A Mexican army drew supplies from places near it and not from government dépôts; and when money failed, as it often did, payments had to be made with drafts on the treasury, which possessed an uncertain value. Hence people often would not part with supplies, the troops went hungry, and the natural tendency toward inefficiency and desertion was accentuated. In order to release the army from service in the interior, when hostilities became imminent in 1845, it was decided to organize volunteer corps; but almost every one, however anxious to see the United States chastised, preferred to let somebody else do the work.[8.1] Mexico, then, did not exactly rise _en masse_ to sweep Taylor away,[8.2] yet the forces gathered at Matamoros could be termed respectable. Arista seems to have had about 175 artillerymen, 3500 infantry, 1100 cavalry, 425 irregular horse under General Antonio Canales and some 500 Matamoros volunteers--in all, say, 5700 men including officers and ineffectives. His first brigade consisted of infantry led by García, a fine man and officer; the second, also infantry, had Vega, a brave and patriotic soldier, for commander; and the third brigade, cavalry, was under Torrejón, who possessed one excellent quality--the instinct of self-preservation. Canales could be described succinctly as a border ruffian and conspirator; and Ampudia, second in general command, was about the same thing plus a cosmopolitan varnish.[8.3] [MEXICAN PREPARATIONS AT MATAMOROS] After news of Taylor's intention to advance reached Matamoros, the Mexicans worked most zealously in constructing fortifications there, and by the end of April had a series of earthworks. Just above the city was erected Fort Paredes, laid out in regular style for 800 men, which guarded the ferry of Las Anacuitas. Two redoubts, crossing their fires, were planted opposite Fort Brown at a distance of seven or eight hundred yards; and two or three minor forts commanded approaches. Gabions or wicker-work strengthened the embrasures, and fascines and sand-bags were freely used. No guns heavier than 12-pounders defended the works, and no platforms were laid; but in general the ordnance was of brass, well cared for though somewhat honeycombed.[8.4]