Heavy fighting took place during World War I due to the city's strategic location on the Sambre. The city was badly damaged with further destruction only being prevented by a treaty agreed with the German forces which required the payment of 10 million Belgian Francs, foodstuffs, vehicles and armaments. Magazine "Spirou", which featured the popular cartoon characters Lucky Luke and the Smurfs, was launched by the publishing company Éditions Dupuis in 1938. After World War II, Charleroi witnessed a general decline of its heavy industry. Following the merger with several surrounding municipalities in 1977, the city ranks as the largest city in Wallonia and the 4th largest in Belgium.