Mercer's "Waterloo Campaign," vol. i., p. 352. For Fleury de Chaboulon's mission to sound Austria, see his "Mems.," vol. ii., and Madelin's "Fouché," ch. xxv.
In the "English Hist. Review" for July, 1901, I have published the correspondence between Sir Hudson Lowe (Quartermaster-General of our forces in Belgium up to May, 1815) and Gneisenau, Müffling, and Kleist. These two last were most reluctant to send forward Prussian troops into Belgium to guard the weak frontier fortresses from a coup de main: but Lowe's arguments prevailed, thus deciding the main features of the war.
"F.O.," France, No. 116. On June 9th the Duke charged Stuart, our envoy at Ghent, to defend this course, on the ground that Blücher and he had many raw troops, and could not advance into France with safety and invest fortresses until the Russians and Austrians co-operated.