Overview
While the tune was composed prior to the Legion's departure for Mexico in the 1860s the lyrics were progressively composed after the Franco-Prussian War, since Alsatians and Lorrains flocked to the legion after these regions were annexed by Germany. The song makes also repeated reference to the fact that the Belgians are "lazy shirkers", this come from the fact that the King of Belgium, who wished to remain neutral in the Franco-German conflict, asked the French governement to not commit the Belgian Legionnaires into the conflict. France agreed to this request and the Belgian Legionnaires remained in French Algeria (the Legion's home), to the dismay of the rest of the Legionnaires. This is why the song says that there's no rolled up blankets (boudin) for the Belgians. The song also mentions the Swiss who constitued the most important foreign contingent of the Legion in the 1870's.
The song relates the feat of arms of the Legion in Tuyen Quang (1884-1885) and in Camerone (1863), which would became the Legion's anniversary.
"Le Boudin" is sung while standing to attention by all ranks of the French Foreign Legion. The Legion marches at only 88 steps per minute, much slower than the 120 steps per minute of all other French military units. Consequently, the Legion contingent at the Bastille Day military parade march brings up the rear. Nevertheless, the Legion gets the most enthusiastic response from the crowd.
Read more about this topic: Le Boudin