The unitarians, then in power at Buenos Aires, naturally sympathised with the leader of their old colorado allies, and were inclined to aid Flores's attempt to regain control of Montevideo. Brazil favoured his pretensions even more actively. The Brazilians of Rio Grande owned most of the land and cattle just over the Uruguayan border, a third of all the rural properties in the republic being taxed to them, and complaints of extortion often came to the Rio government. The blanco president refused the satisfaction demanded, and Brazil determined to enforce the claims of her citizens. Flores was formally recognised as the legitimate ruler of the country, and a fleet and army were sent to his assistance. Lopez, dictator of Paraguay, thought Brazil's intervention in Uruguay dangerous to the international equilibrium of South America. He protested, and when the Brazilian government persisted and sent its army over the border he began war. The Brazilians advanced to Montevideo and their fleet came down the coast. The city was blockaded by sea and besieged by land, while the main body of the allies advanced against the town of Paysandu on the Uruguay River, where the blancos had assembled in force. The place was taken by assault and given up to a horrible pillage, the recollection of which is still graven in the memory of Uruguayans. The blanco party never recovered from the slaughter. Those in Montevideo saved themselves by surrendering the town without resistance. Flores entered in triumph and the blanco leaders fled into exile. Flores was under obligations to lead a division in the war against Paraguay, and he absented himself for that purpose for nearly two years, during which the country districts were somewhat disturbed. In 1867 he returned and restored order with a strong hand. This short lease of undisturbed power was employed in making many important improvements. Great public edifices were completed, the telegraph cable was laid to Buenos Aires, the building of railroads was begun, and a new civil code adopted. Immigration was resumed on a large scale and the country felt the economic impulse that was already transforming the whole Plate valley. Although the country rapidly prospered under the military administration of Flores, the feeling of the blancos remained intensely bitter, and on the 15th of February, 1868, the colorado president was assassinated in the streets of Montevideo.