XI was completed, with an option for an offensive as well as a defensive strategy from the start, to exploit the opportunity created by the improvement in relations between the Third Republic and the Russian Empire. The Franco-Russian Alliance led to Plan XII in February 1892, in which an immediate invasion of Germany was considered possible. But from Plan XI to Plan XVI, the strategy remained defensive-offensive, French attacks being expected after the repulse of a German invasion. In 1888, the French began to study a possible German offensive north of Verdun or through Belgium and Plan XII was written with a contingency for a German breach of Belgian neutrality. In 1904, this was given more attention after a German ( [The Avenger]) sold a copy of the German concentration plan to French intelligence and described mobilisation methods and war plans. Using this windfall and other sources of information, the French adapted Plan XV of 1906, to be ready for a German invasion of Belgium and later plans contained increases in the forces to be assembled to the north and north-east of Verdun. Plan XVI of March 1909, anticipated a German enveloping manoeuvre through Luxembourg and Belgium, after the findings of a 1908 analysis by General Henri de Lacroix, in which he dwelt on the German preference for enveloping manoeuvres and predicted that two German armies would march through eastern Belgium, around the northern flank of the French fortress zone, one to emerge from the Ardennes at Verdun and the other at Sedan. Lacroix wanted to improve the prospects of the usual defensive-offensive strategy by assembling a new Sixth Army near Châlons-sur-Marne, (now Châlons-en-Champagne), west of Verdun, easily to move towards Toul in the centre, Verdun on the left or to the vicinity of Sedan and Mézières behind the northern flank. Prelude Concentration plans, 1911–1914 General Victor-Constant Michel, Vice-President of the in 1910, was more convinced than Lacrois of a German move through Belgium, because of the obstacle of French defences in Lorraine, the terrain in eastern Belgium and German railway building. Michel thought that the Germans would make their main effort in central Belgium and that covering a longer front would need the organisation of French reserve units and integration with the active army. The council rejected his view in 1911, which caused Michel to resign as he considered that deployment from Belfort to Mézières and an offensive towards