Britain ended the Treaty of Amiens and declared war on France in May 1803. Among the reasons were Napoleon's changes to the international system in Western Europe, especially in Switzerland, Germany, Italy, and the Netherlands. Historian Frederick Kagan argues that Britain was irritated in particular by Napoleon's assertion of control over Switzerland. Furthermore, Britons felt insulted when Napoleon stated that their country deserved no voice in European affairs, even though King George III was an elector of the Holy Roman Empire. For its part, Russia decided that the intervention in Switzerland indicated that Napoleon was not looking toward a peaceful resolution of his differences with the other European powers.