era. Power struggle The city was also the center of national and international opium smuggling during the 1920s. In the 1930s, "The Great World" amusement palace was a place where opium, prostitution and gambling came together under the leadership of gangster Huang Jinrong also known as "Pockmarked Huang". Huang was the highest-ranked Chinese detective in the French Concession Police (FCP) and employed Green Gang (Qing Bang) leader Du Yuesheng as his gambling and opium enforcer. The Green Gang became a major influence in the Shanghai International Settlement, with the Commissioner of the Shanghai Municipal Police reporting that corruption associated with the trade had affected a large proportion of his force. An extensive crackdown in 1925 simply displaced the focus of the trade to the neighboring French Concession. Meanwhile, traditional division of society by native place associations was falling apart. The new working classes were not prepared to listen to the bosses of the same native place associations during the 1910s. Resentment against the foreign presence in Shanghai rose among both the entrepreneurs and the workers of Shanghai. In 1919, protests by the May Fourth Movement against the Treaty of Versailles led to the rise of a new group of philosophers like Chen Duxiu and Hu Shih who challenged Chinese traditionalism with new ideologies. Books like New Youth disseminated the new school of thought, while crime and warlord banditry convinced many that the existing government was largely ineffective. In this atmosphere, the Chinese Communist Party was founded in Shanghai in 1921. The Nationalist leader Chiang Kai-shek and the Shanghailanders entered into an informal alliance with the Green Gang, which acted against the Communists and organized labor unions. The nationalists had cooperated with gang leaders since the revolution. Although sporadic fighting between gangsters and communists had occurred previously, many communists were killed in a major surprise attack during the April 12 Incident in the Chinese-administered part of Shanghai. Suspected leftists were shot on sight, so that manyincluding Zhou Enlaifled the city. In the late 1920s and early '30s, large residential areas were built north of the foreign concessions. These residential areas were modern, with good roads and parking lots for automobiles. A new Chinese port was built, which could compete with the Shanghailanders' ports. Chiang Kai-shek continuously demanded large amounts of money from the financial world in Shanghai. Most bankers and merchants were willing to invest in the army, but this stopped