After a confrontation with Erich Ludendorff the Quartermaster general (Erster Generalquartiermeister) of the German Army, Groener was reassigned to a field command.

After resigning from the army in the summer of 1919, Groener served in several governments of the Weimar Republic as minister of transportation, interior and defence.

[1][2] With Erich Ludendorff, Groener worked on the draft for the Hilfsdienstgesetz (Auxiliary Services Act, 1916), which laid down the conscription of men (Arbeitszwang) for the war economy.

This caused confrontations with the third Oberste Heeresleitung (OHL, the supreme command of the German army), led by Paul Hindenburg and Ludendorff.

During the change at the Reichskanzlei in July 1917, when Georg Michaelis replaced Theobald von Bethmann Hollweg as Chancellor, Groener suggested that the state should intervene to limit corporate profits and the wage growth that resulted from booming war-related public demand.

[1] Groener served for six months at the western front first as the commander of the 33rd Division, and then of the XXV Reserve Corps, where he was able to observe trench warfare and the mood of the troops.

[1][2] This task required him to deal with organisational and political challenges, in particular confrontations with the army high command of Austria-Hungary and supervising, then reshuffling, the Ukrainian government which needed help against Bolshevik revolutionaries.

[3] The military situation was becoming untenable and social unrest and rebellion in the German armed forces and the civilian population threatened to break out into revolution.

[2][4]: 51 [3] As the revolution spread through Germany in early November, Groener began to see the Emperor, Wilhelm II, as an impediment to saving the monarchy and the integrity of the army.

On 9 November, when the Kaiser suggested using the army to crush the revolution at home,[4]: 76, 82  Groener advised him to abdicate, because he had lost the confidence of the armed forces.

[2] On the evening of 10 November, Groener contacted the new chancellor, Friedrich Ebert, and concluded the Ebert-Groener pact, which was to remain secret for a number of years.

Ebert agreed to suppress the Bolshevik revolutionaries and to maintain the traditional role of the armed forces as a pillar of the German state; Groener promised that the army would support the new government.

Groener supported signing as he was worried that the unity of the Reich would be in danger if fighting was resumed,[3] contradicting the officer corps and the views of Walther Reinhardt, the Prussian Minister of War.

Groener, who expected to be made a scapegoat, began actively cooperating in this process to save the popular von Hindenburg's reputation, something Ebert immediately noticed.

He started to organise the establishment of the new peacetime (Reichswehr), arguing in favour of a high share of former general staff officers among the new leadership, including in the Reichswehrministerium.

[2] On 8 October 1931 he became acting Interior Minister in the government of Heinrich Brüning and favoured the banning of the Nazi Sturmabteilung (SA storm troops).