Seven Years' War
https://upload.wikimedia.org/wikipedia/commons/thumb/3/30/Seven_Years%27_War_Collage.jpg/300px-Seven_Years%27_War_Collage.jpg (may 17, 1756 – feb 15, 1763)
Originally started as a European War but later ended as a war to secure holding of India and North America. This had positive effects on Britain because they were able to get more land of India and they received additional land in North America. However, with most wars, this definitely also resulted in an economic collapse because it was a very long war. In addition, the amount of workers needed in the European powers increased because of the many people that were stationed away.
Added to timeline:
Economy of the late 17th to the 18th century Europe