At the end of the major spring maneuvers, four soldiers (the "Martin Circus") are tasked by their colonel to clean an armored vehicle called the Invincible which is the pride of the army. One of the four "bidasses" takes the controls and, taking the pretext of an adjustment, starts the engine. Unaccustomed to this type of vehicle, the four young soldiers will be led, in spite of themselves, in an adventure which will end in the open field, for lack of gasoline. Still, they'll have to join the camp with the Invincible. Their resourcefulness will allow them to restart their monster vehicle but it will be to discover a camp deserted by their comrades who have left to reach their base which is 200 kilometers away. Along the way, obstacles of all kinds will considerably slow down their progress - from the involuntary hold-up of a bank to the "armored-stop" practiced by a group of charming Swedish dancers. They will even be robbed of the Invincible while in Paris the authorities decide to remain very discreet about these various incidents of which the flagship of the French cavalry is a victim.