Mr. Washburn to Mr. Seward.

Sir: Since my last despatch, of April 27th, the allied forces have been steadily though slowly advancing upon the soil of Paraguay. At that time the main army had already passed over the river and effected a landing on the Paraguay side. But as they are obliged to take everything with them in the [Page 574] way of supplies, they have been occupied most of the time since in passing over beef, cattle, artillery and cavalry horses, and whatever else may be necessary for the army. The ground on the other side is exceedingly marshy and full of lagunas, or shallow ponds, and while the transports have been engaged in taking over supplies, the troops have been employed in bridging the lagunas and making roads over which the army may advance. In the mean while they are every day getting nearer and nearer the Paraguay encampment. This is at Humayta, and is supposed to be strongly fortified, and it is thought that here the principal battle will be fought. But the strategy of Lopez seems very peculiar to those on this side of the lines. It was supposed he would make great efforts to prevent the landing of the allies, and would certainly inflict great loss upon them before they could establish themselves on the Paraguay territory. But he did nothing of the kind. The allies landed, losing scarcely a man, and Lopez at once fell back, abandoning Fort Itapiru and burning up his encampment. It is not certain, therefore, whether he will risk a general battle or not at Humayta. It would seem that his cause must be lost if he does not hold that position. Since the allies moved up to the Paso de la Patria everything seems to have gone against Lopez. His disastrous attack on the island opposite Itapiru, of which I made mention in my last, was of a character similar to another assault on superior forces made two days ago. On this last occasion he sent at mid-day some four or five thousand troops to surprise the outposts of the allies. The forces he encountered were the veterans of General Flores, from Uruguay, and for a moment the latter were compelled to fall back; but General Mitre at once ordered up such heavy re-enforcements that the Paraguayans were swept away like chaff. Of the five thousand engaged in the action, it is claimed that three thousand are killed, wounded, or prisoners. The loss of the allies is admitted also to be heavy, but not half that of the Paraguayans. Such severe and successive losses must seriously weaken the army of Lopez, and render still greater the disparity between his forces and those of the allies. It seems now that a decisive action must be fought within a very few days. General Mitre, however, is moving deliberately, as if conscious of his superior strength, and as though he knew he must win, unless provoked into some rash or precipitate act. Hence the day of the final struggle may be more distant than is generally supposed. Yet here there is no difference of opinion as to what will be the final result.

I have the honor to be, sir, your most obedient servant,

CHARLES A. WASHBURN.

Hon. William H. Seward, Secretary of State, Washington, D. C.