Neutrality is a traditional and essential part of the European state system, allowing states to remain aloof of an armed conflict. The Congress of Vienna (1814-1815) elevated Switzerland and the Low Countries, two contentious buffer regions on the continent, to the status of “permanent” and externally guaranteed neutral zones. Neutrality would thus lose its status as a temporary national policy choice and become intertwined with the essential preconditions of statehood and independence (Edouard Descamps, La neutralité de la Belgique, Larcier, 1902). Obligations limiting the guaranteed states’ sovereignty were the necessary counterpart of their tranquil existence at the heart of Europe, including their commercial potential. The nature of third party-obligations towards the guaranteed states was the subject of a hot debat a posteriori, not the least in view of the German invasion of Belgium in August 1914. Violating Belgium’s neutrality equalled starting an armed conflict. The sanction of war was thus war, which logically terminated Belgium’s neutral status, since the country became a belligerent once attacked. Was “permanent” neutrality then anything new at all ? If looked closer at antecedents in international history, geopolitical factors determined buffer states’ fate. The 1899 and 1907 Hague Conventions initiated a codification, but the main principles governing neutrality were still those traditional law of nations doctrine. Maartje Abbenhuis’s and Isabel Hull’s recent works (An Age of Neutrals, CUP, 2014/A Scrap of Paper, Cornell UP, 2014) have brought a subject traditionally seen as already “well-researched” back to the forefront. My approach starts from the position of Belgium as a geopolitical object, conceptualized in legal language by diplomatic practitioners, a demarche analogous to that of Thomas G. Otte (The Foreign Office Legal Mind, CUP, 2011). My focus lies on France and Britain, as generators of Belgian independence in the 1830s, and concentrates on archival material collected in Paris, London ...