Val�r, managed to direct Catholic Spaniards against the city in order to initiate a Counter-Reformation. In 1624, a "re-Catholicization" law was enacted, and churchgoing was strictly controlled. In 1628, the city council filed against this at the Reichskammergericht. Maria had to flee to Cologne when the Dutch stormed the city in 1629. She returned in the summer of 1631 following the Bavarians under Gottfried Heinrich Graf zu Pappenheim, only to leave again in September. She died 1644 in Cologne.
The war proved a severe blow to the city, with frequent arrests, kidnapping and rape. Even after the Peace of Westphalia from 1648, troops remained in the city until 9 September 1650.
The first historic evidence of the important mining tradition of Essen date back to the 14th century, when the princess-abbess was granted mining rights. The first silver mine opened in 1354, but the indisputably more important coal was not mentioned until 1371, and coal mining only began in 1450.
At the end of the 16th century, many coal mines had opened in Essen, and the city earned a name as a centre of the weapons industry. Around 1570, gunsmiths made high profits and in 1620, they produced 14,000 rifles and pistols a year. The city became increasingly important strategically.
Resident in Essen since the 16th century, the Krupp family dynasty and Essen shaped each other. In 1811, Friedrich Krupp founded Germany's first cast-steel factory in Essen and laid the cornerstone for what was to be the largest enterprise in Europe for a couple of decades. The weapon factories in Essen became so important that a sign facing the main railway station welcomed visitor Benito Mussolini to the "Armory of the Reich" in 1937. The Krupp Works also were the main reason for the large population growth beginning in the mid-19th century. Essen reached a population of 100,000 in 1896. Other industrialists, such as Friedrich Grillo, who in 1892 donated the Grillo Theatre to the city,
