The Netherlands continued the policy of neutrality during World War I. This stance arose partly from a strict policy of neutrality in international affairs that started in 1830 with the secession of Belgium. Dutch neutrality was not guaranteed by the major powers in Europe however, nor was it a part of the Dutch constitution. The country's neutrality was based on the belief that its strategic position between the German Empire, German-occupied Belgium, and the British guaranteed its safety. The Dutch military strategy was aimed exclusively at defence and rested to a large extent on the Dutch Water Line, a defensive ring of rivers and lowland surrounding the core Dutch region of Holland, that could be inundated.