and reduced tax revenue. Essentially, invasions caused long-term damage to the provincial tax base, which lessened the Empire's medium- to long-term ability to pay and equip the legions, with predictable results. Likewise, constant invasions encouraged provincial rebellion as self-help, further depleting Imperial resources. Contrary to the trend among some historians of the "there was no fall" school, who view the fall of Rome as not necessarily a "bad thing" for the people involved, Ward-Perkins argues that in many parts of the former Empire the archaeological record indicates that the collapse was truly a disaster. Ward-Perkins' theory, much like Bury's, and Heather's, identifies a series of cyclic events that came together to cause a definite decline and fall. Transformation Henri Pirenne In the second half of the 19th century, some historians focused on the continuities between the Roman Empire and the post-Roman Germanic kingdoms rather than the rupture. In Histoire des institutions politiques de l'ancienne France (1875–89), Fustel de Coulanges argued that the barbarians simply contributed to an ongoing process of transforming Roman institutions. Henri Pirenne continued this idea with the "Pirenne Thesis", published in the 1920s, which remains influential to this day. It holds that even after the barbarian invasions, the Roman way of doing things did not immediately change; barbarians came to Rome not to destroy it, but to take part in its benefits, and thus they tried to preserve the Roman way of life. The Pirenne Thesis regards the rise of the Frankish realm in Europe as a continuation of the Roman Empire, and thus validates the crowning of Charlemagne as the first Holy Roman Emperor as a successor of the Roman Emperors. According to Pirenne, the real break in Roman history occurred in the 7th and 8th centuries as a result of Arab expansion. Islamic conquest of the area of today's south-eastern Turkey, Syria, Palestine, North Africa, Spain and Portugal ruptured economic ties to western Europe, cutting the region off from trade and turning it into a stagnant backwater, with wealth flowing out in the form of raw resources and nothing coming back. This began a steady decline and impoverishment so that by the time of Charlemagne western Europe had become almost entirely agrarian at a subsistence level, with no long-distance trade. Pirenne's view on the continuity of the Roman Empire before and after the Germanic invasion has been supported by recent historians such as François Masai,