The second Paraguayan column , 4000 men led by Col. Francisco Isidoro Resquín , penetrated a region south of Mato Grosso , and sent a detachment to attack the military frontier post of Dourados .
The second Paraguayan column , formed from some of the 4,650 men led by Col. Francisco Isidoro Resquín at Concepcion , penetrated into Mato Grosso with 1500 troops . 
 He then sent a detachment to attack the military frontier post of Dourados .