The pass of Obligado, on the River Parana, was the position selected for obstructing the passage of the English and French vessels employed in completing the blockade of the province of Buenos Ayres, by cutting off its communication with the provinces on the opposite bank. A blockade of the capital only of Buenos Ayres, and of its River Plate shores would, of course, be nugatory unless enforced along the course of the Parana as far as the limits of that province extend. Reinforcements of troops, horses, artillery, and warlike stores of all sorts, would continue to be sent across the Parana into the province of Entre Rios, from whence continually to renew and supply the Buenos Ayrean army invading the Banda Oriental and besieging Monte Video. To prevent this and ultimately cause a cessation of these disastrous hostilities it was necessary to blockade the whole fluvial coast of the province of Buenos Ayres. In order, therefore, to effect this blockade a small combined squadron of French and English vessels was detached from the force in the River Plate to occupy the Parana, as far as the effectual enforcement of the blockade of the province of Buenos Ayres might require. The boundary between the province of Buenos Ayres and that of Santa Fé strikes the Parana at the ‘Arroyo del Medio.’ This division, marked by a brook running into the river, is about thirty or forty miles above the turn in the Parana, called the ‘Vuelta de Obligado,’ which it was of course necessary to pass in order to reach the limits of the province. It was determined by the Government of Buenos Ayres to prevent the combined squadron from proceeding beyond the pass of Obligado if possible. But although the preparations for defence could not but have been known to hundreds, long previous to the declaration of the blockade, as well as the fact of works being in progress for barring the passage, the construction of batteries, and placing the chain cables, vessels, &c., all of which must have occupied much time, it is remarkable that no information whatever as to the plan or real nature of the intended obstruction could be obtained either at Buenos Ayres or Monte Video. Vague rumours did reach the admirals commanding in chief, and other officers, of preparations in progress, but some reported that vessels were sunk in the channel, others said that forts or batteries were in course of construction at every commanding point on the river; in fact, the true nature of the intended resistance was entirely unknown, until some boats which preceded the squadron when proceeding up the river were fired upon a few miles below Obligado, at a place called San Pedro. And even then it was not believed that any serious opposition would be attempted to the advance of the blockading flotilla. However, when once the fire had been opened by the Buenos Ayreans at Obligado it became of course necessary to return it, and the result was the general engagement that ensued. When it is recollected that the scale on which the defences had been prepared was quite unexpected, and that the Buenos Ayrean force employed was much greater than was anticipated (amounting to about 4,000 men), while the nature of the other obstacles to be encountered was previously unknown, it will be evident that the skill and experience of the able officer who commanded the squadron were put to a severe test, and that it required his well concerted arrangements in the plan of attack and the gallantry displayed in carrying them into effect, to obtain the successful result that added to the high professional reputation of Sir Charles Hotham, already too well known to need any tribute here. It must also be borne in mind, in order to form a just estimate of this successful engagement, that with the exception of the steamers and a corvette, the major part of the force consisted of a mere flotilla of small vessels, armed for the purpose of ascending the river, and that they were for several hours exposed at no great distance to a heavy and well-directed fire from formidable and skilfully planned batteries. It is, however, needless here to give any detailed description of the action that resulted in the destruction of the batteries and other defences at this place. The despatches of the commanders of the English and French squadrons, Sir Charles Hotham and Admiral Tréhouart, were published at the time, and give a clear account of the manner in which the affair was conducted, showing the skill and great gallantry manifested generally throughout this affair.