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 organized as corps befitting a modern army, are next presented. The artillery that was totally militarized and its materiel modernized 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 France, troops that were considered part of the army were specifically concerned with controlling bandits and applying the law under the command of a Marshal. Their original name of archers remained long after they adopted firearms and they could be found in all parts of France. They still are today, but under the name of gendarme in most countries. They were often veteran soldiers and this section will also feature what punishments a soldier could expect when condemned of some wrongdoing.Many towns and cities had their own regular local troops on duty as garrisons and security corps and we describe a number of these well appointed and effective soldiers, some of whom saw action.A fairly large section is devoted to the reserve forces. France had three types of militias. The best-known is the 1688 Royal Militia, which was the first integrated system leading to what became national conscription for military service in the regular armies. Next to unknown are the Coast Guard Militia organization that might might muster 150,000 men and, most of all, the Bourgeois Militia in all the cities and towns of the realm that probably amounted to some half a million men, many of them well armed and uniformed. This section includes a number of notices describing the Bourgeois Militias and their Privileged companies showing an almost totally unknown sedentary "territorial" army that performed well in the few times when some were called upon.The last section will be a look at the social life of soldiers, their "families", camp followers and and sutlers. There were many women and children in the wake of regiments, as prints show and some documents elude, but they were not officially recognised in the army yet should not be forgotten.