Major Demeziere Sonnen was an accomplished artillery instructor for the Principality of Zeon's armed forces in the years leading up to the One-Year War. However, when mobile suits were introduced as standard combat units, Demeziere Sonnen tested poorly as a pilot. He could only sit by and watch as his students left and became mobile suit pilots. During this time, Sonnen's usefulness was in question as artillery took a decreasing role in combat in light of the power and versatility of mobile suits. Eventually, Sonnen suffered a sort of breakdown. He recovered from the breakdown, but was beset by constant tremors that he kept under control with dope medicine he always kept on his person and would often be found with it in his hand.
