When the uprising of 1823 failed so signally, a number of the refugees who escaped prosecution fled to Mexico and Colombia. There was a settlement of these people in Caracas. They turned to "The Liberator" for support, and soon the invasion of Cuba, by a force composed of Mexicans and Colombians, either under the personal leadership, or under the direction of Bolivar, was planned. The leaders of this movement also sought aid in the United States. Now the slaveholders of the South were at this time opposed to the separation of Cuba from Spain, because under the lead of Bolivar it would mean the doom of the slave trade, the abolition of slavery, and such an achievement in Cuba would be inimical to their own interests. So the attempt to procure assistance in the United States was really the cause of the failure of the proposed expedition. Spanish spies were quickly informed of the proposed plan, and such strenuous efforts were openly made to make such an attempt ineffective, that it was never made. Bolivar had all he could attend to in South America, and he was too intelligent a leader to attempt the impossible, and at the same time leave his plans for the liberation of South America to meet certain defeat in his absence. But Spain did not easily overlook the conspiracy, and she seized the leaders in Cuba who were conspiring with those in Colombia and Mexico. Two young men of fine families, Don Francisco de Aguero Velasco and Don Bernabe Sanchez, were apprehended by the aides of the Captain-General, imprisoned and most cruelly treated, and when their spirit was not broken by torture and they refused to divulge the secrets of their leaders, they were condemned to die for treason, and paid the penalty of their patriotism with their lives.