BARRIER TREATY, the name given first to the treaty signed on 29th of October 1709 between Great Britain and the states-general of the United Netherlands, by which the latter engaged to guarantee the Protestant succession in England in favour of the house of Hanover; while Great Britain undertook to procure for the Dutch an adequate barrier on the side of the Netherlands, consisting of the towns of Furnes, Nieuport, Ypres, Menin, Lille, Tournai, Condé, Valenciennes, Maubeuge, Charleroi, Namur, Halle, Damme, Dendermond and the citadel of Ghent. The treaty was based on the same principle of securing Holland against French aggression that had inspired that of Ryswick in 1698, by the terms of which the chief frontier fortresses of the Netherlands were to be garrisoned by Dutch troops. A second Barrier Treaty was signed between Great Britain and Holland on 29th of January 1713, by which the strong places designed for the barrier were reduced to Furnes, the fort of Knocke, Ypres, Menin, Tournai, Mons, Charleroi and the citadel of Ghent, and certain fortresses in the neighbourhood of that city and of Bruges; Great Britain undertaking to obtain the right for the Dutch to garrison them from the future sovereign of the Spanish Netherlands. Its terms were included in the treaty of Rastatt, between the emperor and France, signed on the 7th of March 1714. A third Barrier Treaty was signed in November 1715.
See Jean Dumont, Corps universel diplomatique, &c. (1726–1731), vol. viii.