Complex sentence: Baldorioty de Castro founded the "Partido Autonomista" in 1887, but he was only able to work within it for a few months before being imprisoned in Fort San Felipe del Morro, after being accused of publishing propaganda that affected the Spanish government's image.
Split into simpler sentences: Baldorioty de Castro founded the "Partido Autonomista" in 1887, but he was only able to work within it for a few months. He was tried and imprisoned in Fort San Felipe del Morro, after being accused of publishing propaganda that affected the Spanish government's image.