During this period, as has been said, the Argentine statesman, Rivadavia, was working whole-heartedly towards the intellectual betterment of his country, and in this he was assisted by Alvear and others. But the warlike stress of the period cut short the majority of these endeavours. The Brazilians, anxious to conclude the war, had brought down their entire fleet to the River Plate, and they were blockading the entrance to the river and the port of Buenos Aires. At the sight of the hostile vessels the local differences were for the time being laid aside, and, war vessels being an urgent necessity, public subscriptions were eagerly forthcoming for the purchase of these. The small Argentine fleet, when completed, was placed under the orders of that gallant Irishman, Admiral Brown, and the naval leader lost no time in forcing his attacks home upon the hostile fleet. Owing to the fury of these, the efficiency of the blockade was destroyed, although the Brazilian vessels continued in the neighbourhood for some while. General Alvear was now appointed commander of the land force operating against Brazil, and in conjunction with the Uruguayan General, Lavalleja, he assumed the aggressive, defeated the Imperial army, and was in turn about to invade the Brazilian province of Rio Grande, when he found himself obliged to abandon the project owing to the want of horses from which his army suffered. In 1827 Rivadavia's Government fell, and after a while Manuel Dorrego, a gifted soldier and politician, found himself at the head of the State. Peace was now signed with Brazil, but on terms which the great majority of the Argentines resented bitterly, and the unrest in the Republic rapidly came to a head. Dorrego was opposed by General Lavalle, one of the most famous personalities of the period. Both parties resorted to arms. Dorrego's force was defeated and its leader captured. On this Lavalle, a brilliant and liberal-minded man, committed the gravest error of his career--one, moreover, the nature of which was entirely foreign to his character--for, after capturing Dorrego, he executed his prisoner. Reasons of State were the cause of this political crime, since no personal animosity was involved.