Following a successful operation at Merkem in April 1918, Michiels was made a Commander of the Legion of Honour by Ferdinand Foch.

[1] In March 1919 Michiels became a professor at the Instruction Center of Staff (later the War College, part of the Royal Military Academy), where he would work for nearly 12 years.

In June 1937 Michiels was promoted to major general and made head of the personnel department of the Defence Ministry.

[1] Following the outbreak of World War II in September 1939, Michiels took command of the 7th Infantry Division to oversee its mobilization.

During the Belgian Army's last stand at the Battle of the Lys on 27 May, Michiels suggested that the king send a representative to the Germans to negotiate a ceasefire.

The Germans inquired him on Belgium's observance of neutrality before the invasion and on the Mechelen incident, but he refused to offer them any answers.

The Germans offered to return him to Belgium in 1943 and hand him control of the National Office of Veterans Affairs, but he refused on the account that he would be leaving his subordinates behind.