Cromwell's early life is known though some theorize that he was once a priest as his overall goal of conquering the Holy Land is very much in line with the ultimate goal of the Brimiric church. At some point though he was contacted by King Joseph of Gallia (possible through Sheffield) and gave him his secret support to overthrow the monarchy. Ecstatic, Cromwell would create his new organization by bringing together dissatisfied commoners, and ambitious nobles. Together they would successfully take control of Albion, exterminate the Tudor bloodline, and chase the Royalists to Newcastle. There he would task his agent, the Viscount Wardes, to assassinate the Crown Prince Wales and retrieve letters that would sever the potential relationship between Tristain and Germania. The plan worked, the Prince was slain, the letters were his, and all of Albion was under his control. Flush with victory Cromwell would reorganize his new country into a Holy Republic with himself as its Holy Emperor.
Following his coronation Cromwell used the Ring of Andvari to implant a false spirit within the body of Wales. He then ordered his new puppet to kidnap Princess Henrietta in order to leave Tristain without a leader. The plan worked up to a point, until a rescue team lead by de Valliere and Saito Hiraga stopped the duo and defeated the corrupted Prince one last time. Nonplussed by this, Cromwell called for the invasion of Tristain as part of Reconquesta's overall goal of conquering all of Halkeginia and reclaiming the Holy Land. Armed with a superior navy and the element of of surprise, Albion was quickly able to bypass Tristain's coastal defenses and attack Tarbes, a village that would serve as the staging point for their main attack.
Despite enjoying some initial success, the invasion would end in disaster when Hiraga and de Valliere, armed with a restored Zero-Fighter, slew all of his dragon-knights, the accompanying ex-Viscount, and destroyed his invasion fleet. Bereft of his fighting force Cromwell attempted to flee but was confronted by Guiche de Gramont, Kirche von Zerbst, and Tabitha. Still armed with the Ring of Andvari, the fallen Emperor would attempt to turn the trio into his slaves only for Gramont to knock him out with a fallen branch. Defeated and humiliated, Cromwell was imprisoned by Tristain and set to be tried when Sheffield, under Joseph's orders, stole his ring and killed him in his own cell,.