This fourth and final part of our study concentrates on the early 18th century War of Spanish Succession. It was the largest and most difficult conflict in Europe since the Thirty Years War and unsurpassed until the Napoleonic Wars. It started because of Bourbon France and Habsburg Austria’s conflicting candidates to the Spanish that soon involved other nations such as Great Britain and the Netherlands. It was mostly fought on three fronts: Flanders, northern Italy and Spain. Due to various factors, it proved to be a very difficult period for the Sun King. During the first decade, there were repeated and massive defeats in Flanders and Germany where French princes and marshals proved to be unequal to the genial Duke of Marlborough and the competent Prince Eugene. The hard-pressed French forces in the northern Italian front eventually collapsed in 1706. The Spanish front, although it started badly for Felipe V, the French pretender, things improved and the allied troops supporting the Austrian Carlos III were decisively defeated in 1707, again in 1710 and finally at Barcelona in 1714. Meanwhile, following the hard fought battle at Malplaquet, the main French armies, that were amazingly resilient reflecting the nation’s tenacity from the Sun King to the humblest folks, now had some success under Marshal Villars culminating in the strategic 1712 victory at Denain. This led to many previous allied gains now being lost. This was happening when Great Britain basically withdrew its support for the war. The treaties signed from 1713 basically gave the Sun King and France what it most wanted: Felipe V as King of Spain and its empire. It was a hard fought conflict but, in the end, France won.