Complex sentence: He learned of Rovira's coup on 12 April, but did not put his army in motion until the 20th, when it issued from Tarragona with the 6,000 foot soldiers and 800 cavalry belonging to General Pedro Sarsfield's division and part of Eroles' division.
Split into simpler sentences: He learned of Rovira's coup on 12 April, but did not put his army in motion until the 20th. On that day it issued from Tarragona with 6,000 foot soldiers and 800 cavalry belonging to General Pedro Sarsfield's division and part of Eroles' division.