17th century Europe was dominated by the struggle between the Bourbon kings of France, and their Habsburg rivals in Spain and the Holy Roman Empire. Until the mid 20th century, the Thirty Years War was primarily seen as a German religious conflict; in 1938, historian CV Wedgwood argued it formed part of a wider, ongoing European struggle, with the Habsburg-Bourbon conflict at its centre. Modern historians sometimes refer to the Franco-Spanish War as a 'declared war', which represents only one phase of an ongoing contest, with many different locations and participants.