At 450,000 sq. km, the kingdom of Henri IV covered some four-fifths of modern-day France. Despite everything, given the era and taking into account the heterogeneousness of the lands that made it up, the territory administered by the king was enormous.
One must remember that the horse was the most common means of transport. A person on horseback could cover some 40 to 50 kilometres a day, on roads that were often in poor condition and dotted with toll collectors. Charles Estienne, the author of Le guide des chemins de France (Guide to the Roads of France – 1552), estimated that an ordinary rider would need 19 days to travel from the north of the kingdom to the south, and 22 days to go from east to west. From Paris, a journey on horseback to Bordeaux required seven days. Eight to ten days were needed to reach Lyon, and sixteen to twenty days to get as far as Marseille. In many respects, therefore, France in the 16th century was much larger than the entire European continent appears to a French person today. One can better understand how difficult it was to govern this territory – which also had a wide variety of languages and cultures – and why Henri IV and his entourage wanted to streamline its administration.
Even though France's present-day hexagonal shape was visible even then, the kingdom's borders were different than those we know today. Some regions that are now part of France were not yet part of the kingdom, and several foreign enclaves were scattered across French soil. Calais was purchased from the English in 1564 by Catherine de Médicis, but was then re-occupied – this time by the Spanish – between 1596 and 1598. Comtat Venaissin remained a papal enclave until 1791, and the Principality of Orange passed in 1544 to William the Silent from the House of Nassau, leader of the United Provinces (the modern-day Netherlands).
Within its borders, an inextricable tangle of territories with different statuses made centralising the country's administration extremely difficult. First, there were the crown lands. These were lands that belonged directly to the king, and which were supposed to provide revenues to support him. Crown lands could not in theory be sold, but sometimes a king in need of money would sell a part of them.
Parts of France consisted of appanages – properties detached from the crown lands and given by the king to his younger children. The benefits derived from these allowed them to maintain their lifestyle and support their clients. Upon the death of François, the brother of Charles IX and Henri III in 1584, Henri de Navarre was given the duchy of Alençon.
Finally, there were fiefdoms that belonged to the great families. These lineages sometimes took offence at the might of the king, when strategic marriage alliances united these lands to form powerful territorial ensembles.
Thus, when Henri de Navarre acceded to the throne, he was the ruler of an impressive number of properties that he had inherited from his ancestors. By uniting the legacies of the House of Foix-Albrets and the House of Bourbons-Vendôme, and by being the ruler of the State of Navarre, Henri became what English historians call an "overmighty subject". Such concentrated power could be seen as a threat by the king of France, but the lack of a male heir to the last of the Valois – which resulted in the king of Navarre being offered the throne – eliminated this danger.