This was a German unrealised plan prepared under the supervision of Generalmajor Erich von Manstein, of the operations staff of the general staff, for defensive/offensive operations as part of a two/three-front war with Czechoslovakia in 'Grün' (i), and France and Poland in 'Blau' (i) (1935/37).
'Rot' (i) was the first German deployment scheme prepared since the end of World War I apart from the planning for a number of small-scale operations to be implemented in the event of any Polish invasion of Germany’s eastern region in the late 1920s.
'Rot' (i) was designed to meet a major French offensive in the western part of Germany at a time when the Czechoslovaks, although assisting the French, were not playing a strongly offensive role. The hostility of Poland was not deemed inevitable because of the non-aggression treaty recently concluded between Germany and Poland: it was thought by the German planners that Poland would wait to see the course of military operations before committing herself.
The two most likely French thrusts were thought to be either through the Kraichgau, between the Schwarzwald and the Odenwald, with the object of linking with Czechoslovak forces to separate the northern and southern parts of Germany, or through the Ruhr industrial region to paralyse Germany’s industrial heart. To meet this situation, the German land forces were to be divided into four armies, three of them deployed in the west and the fourth, with the Grenzschutz (border defence force), covering the Czechoslovak and Polish frontiers. It was not intended to offer any serious resistance to the French in the region to the west of the Rhine river, but a strong attempt was to be made to bring the French action to a halt on the line of the Rhine river itself.
This original 1935 version of the plan was therefore based on the premise of a defensive war against Czechoslovakia and Poland while defeating a surprise invasion by France.
The definitive 1937 version of the plan was based on an offensive war with Czechoslovakia with the object of preventing Germany from becoming involved in a protracted two-front war.