As the summer wore away, Maximilian, under Mr. Seward's policy, gained in strength till finally all the accessible sections of Mexico were in his possession, and the Republic under President Juarez almost succumbed. Growing impatient at this, in the latter part of September I decided to try again what virtue there might be in a hostile demonstration, and selected the upper Rio Grande for the scene of my attempt. Merritt's cavalry and the Fourth Corps still being at San Antonio, I went to that place and reviewed these troops, and having prepared them with some ostentation for a campaign, of course it was bruited about that we were going to invade Mexico. Then, escorted by a regiment of horse I proceeded hastily to Fort Duncan, on the Rio Grande just opposite the Mexican town of Piedras Negras. Here I opened communication with President Juarez, through one of his staff, taking care not to do this in the dark, and the news, spreading like wildfire, the greatest significance was ascribed to my action, it being reported most positively and with many specific details that I was only awaiting the arrival of the troops, then under marching orders at San Antonio, to cross the Rio Grande in behalf of the Liberal cause.
Ample corroboration of the reports then circulated was found in my inquiries regarding the quantity of forage we could depend upon getting in Mexico, our arrangements for its purchase, and my sending a pontoon train to Brownsville, together with which was cited the renewed activity of the troops along the lower Rio Grande. These reports and demonstrations resulted in alarming the Imperialists so much that they withdrew the French and Austrian soldiers from Matamoras, and practically abandoned the whole of northern Mexico as far down as Monterey, with the exception of Matamoras, where General Mejia continued to hang on with a garrison of renegade Mexicans.
The abandonment of so much territory in northern Mexico encouraged General Escobedo and other Liberal leaders to such a degree that they collected a considerable army of their followers at Comargo, Mier, and other points. At the same time that unknown quantity, Cortinas, suspended his free-booting for the nonce, and stoutly harassing Matamoras, succeeded in keeping its Imperial garrison within the fortifications. Thus countenanced and stimulated, and largely supplied with arms and ammunition, which we left at convenient places on our side of the river to fall into their hands, the Liberals, under General Escobedo—a man of much force of character—were enabled in northern Mexico to place the affairs of the Republic on a substantial basis.