But a far more serious danger was threatening the empire in the North. On April 9, 1865, General Lee surrendered to the Federal army. The Civil War in the United States was at an end, and the French were beginning to understand that the Northern republic, whose unbroken unity stood strengthened, could no longer remain a passive spectator of the struggle taking place at its frontier. The scene of military interest suddenly shifted to the Rio Grande, and the incidents happening on the border deserved more attention than Maximilian seemed at first inclined to bestow. The interests of the national party were represented in Washington by Senor Romero, who, with consummate tact and ability, made the most of every opportunity. The service rendered by him to the cause of republicanism and of Mexican independence was second to none in importance. No detail seemed too trifling to be turned to account in his effort to strengthen the Mexican cause with our government. A rumor reached us that President Juarez had succeeded in raising a loan in the United States. The ranks of the Liberal army were receiving important reinforcements from the officers and men of General Banks's command, who passed the border in large numbers to take part in the attack of General Cortinas at Matamoros. Already, in January, 1865, the impulse given to the Republican party in the North vibrated throughout the land. Soon resistance everywhere appeared in arms once more. Both General Mejia and Admiral Cloue, then in command of the French Gulf Squadron, complained that the United States army afforded protection to the Juarists. Recruiting-offices had been opened in New York, which, although not countenanced by the government, must have furnished valuable auxiliaries to the Liberals. Alarming rumors reached France and Mexico with regard to the extent of the movement. On the other hand, the negotiations then being carried on between Napoleon and Maximilian, with a view to securing the Mexican debt to France by a lien upon the mines of Sonora, were causing uneasiness in the United States, and gave rise to considerable diplomatic correspondence.* * See, in this connection, "Diplomatic Correspondence," 1865, Part III, pp. 357-363, 417, and letter of Secretary Seward addressed to Mr. Bigelow, February 17, 1865.