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. The study then discusses the economic and the serious climactic effects notably brought about by the awful winter of 1708-1709 in France that was also severe in other countries.The economic pressure was enormous on the Sun King's government, but it finally managed to go through it thanks to the amazing resilience of the French economy.French histories often state it was catastrophic, yet Britain's economy had a national debt rising up to four times faster than France's and this was obviously a factor in Britain's withdrawal from the alliance. The French army's technical and support services, many of which were the first to be organised as corps befitting a modern army, are next presented.The artillery that was totally militarised and its materiel modernised to standards copied by all other nations.Engineering under the guidance of Marshal Vauban became peerless and imitated in all nations.Up to the Sun King's time, old and crippled veteran soldiers were left to a pauper's miserable survival; he first introduced a pension system and, in the 1670s, had the splendid Invalides hospital built in Paris to care for these soldiers.We will also glance at what religious personnel was attached to army units and hospitals to care for soldiers broken bodies and souls. Since Medieval times in...