He was awarded the rank of staff captain and was assigned as an officer to the 6th Haná Rifle Regiment of the Czechoslovak Legions in Russia.

After Hitler's victory in the 1932 German presidential election as Reich Chancellor in 1933, and the failure of the 1932 Geneva Disarmament Conference, it was necessary to prepare the army for a possible military conflict.

He replaced the dismissed Jan Syrový in his highest position, to whom he supported Edvard Beneš and the French military mission established a substitute post of inspector general.

Later, after Masaryk's abdication of the presidency, disputes arose over the competencies of the chief and the inspector, which, however, he placed as a matter of trust in his person, and Syrový had to resign in a representative position.

[12][13] As the highest-ranking soldier, from 1 March 1938 to September 1938, he pushed for an increase in the number of army in peacetime by continuously calling up midfielders for training.

After the occupation of Austria on 12 March 1938, the mobilization plan VI modified by the General Staff was completed in April 1938 while the German Wehrmacht was not able to make a similar adjustment until September 1938.

[14] After intelligence announced the concentration of German troops in Saxony, northern Austria and southern Silesia, after consultation with the President and the government, one year of an advance for an extraordinary exercise was called, and from 22 May to 13 June 1938 a border guard was declared to ensure the protection of the republic until a possible general mobilization.

[15] At the beginning of September 1938, he addressed a memorandum to politicians, warning against concessions to Nazi Germany and drawing attention to the army's readiness to fight.

On the border, from 12 and 13 September, the Czechoslovak government declared martial law in response to an armed uprising organized by the Sudetendeutsche Partei, which had to be suppressed by the army's emergency and, eventually, regular units.

Krejčí made another request for mobilization at a meeting with the president against the concentrated German army on 21 September, and again Beneš was not heard.

An agreement on the withdrawal of the borderland from Germany was adopted in Munich on the night of 29 September and delivered, as automatically accepted, to the Czechoslovak government.

[21]At the beginning of October, he was at the forefront of pressure on politicians in favor of military defense, as he was convinced of the readiness and determination of the army.

[23] After the beginning of the German occupation of Czechoslovakia in March 1939, he lived in Prague , later he was forced to move to his wife's birthplace in Jablonné nad Orlicí.

He worked as an auxiliary worker in a nationalized button factory in Jablonné nad Orlicí, formerly belonging to his wife's family.

He died as a simple soldier on 9 February 1972 in the Ústí nad Orlicí Hospital and was buried in his native town of Brno-Tuřany with legionary honors.

In 1999, the "Brno Legionnaire" edition published the first publication about this general, prepared at the request of the family according to available materials, entitled " Ludvík Krejčí, Tuřanský generál".

[25] On 28 October 2017 the President of the Republic, Miloš Zeman, in memoriam bestowed on him the Order of the White Lion[26] of the 1st Class Military Group for extraordinary merits for the defense and security of the state.