caused a change in Centralist military plans. Arista judged the sudden appearance of the Texan flagship at this point as indicative of a joint naval and military offensive operation against Matamoros in conjunction with Canales.[53]  Arista's conclusion seemed to be supported by a report at Matagorda on October 10, that Commander Ribaud of the southern Mexican Federalists had been "a few days since in Corpus Christi Bay concerting action with Canales."[54]

It was not long before reports began to reach Matamoros that the advance units of Canales' forces had commenced their march for the Río Grande. Arista, accordingly, left Matamoros on September 16 with seven hundred cavalry, a strong division of infantry (numbering in all one thousand men), and four pieces of artillery to protect the Villas del Norte.[55]  He moved in the direction of Mier. Colonel Mendoza was ordered to San Fernando de Rosas with a respectable force, and General Reyes, who had been at Mier with the Second Division (nine hundred men)[56]  since September 7 left there on September 20 in pursuit of Molano. On the 21st Arista was at Reinosa Viejo, on the 22nd at Camargo, and on the 23rd was reported at the Arroyo San Pedro, five days journey from Monterey toward which place he was directing himself at forced marches to intercept Canales, who had crossed the Río Grande and the San Juan, and was advancing toward China, now pursued by General Reyes. The area between Presidio del Río Grande and Laredo was protected by the cavalry of Lieutenant Colonel Galán, commander of the frontier presidial companies (three hundred men).[57]  The heavy rains of mid-September impeded military operations. On the 28th[58]  Arista reached Concepción, approximately midway between Cadereyta and China on the north bank of the San Juan River, where on the 29th he was joined by the forces under Reyes and Vasquez,