Three years later, Mother Courage and Kattrin fold washing on a cannon. At the same time, Courage bargains with an Ordinance Officer over a bag of bullets. Swiss Cheese, now in a paymaster's uniform, and Yvette Pottier, the camp prostitute, look on. Yvette's red boots stand nearby.
Courage declares that she will not buy military property, reproaching the officer for selling ammunition when his soldiers have nothing to shoot with. The officer encourages her to sell them to another regiment and Courage buys the bullets. Giving Swiss Cheese his underwear, Courage enjoins her son to balance the regiment books. Even if the seasons do not come, the books must balance. He leaves with the Officer.
Courage remarks to Yvette that the war is drawing in more countries, thus her business prospects improve as well. Yvette is desperate because of rumors that she is ill and none of the men will touch her. She starts recounting a familiar story of her Dutch army beau, Peter dubbed Piper for the pipe he always carried in his mouth. The story should harden Kattrin against love. Yvette sings it in "The Fraternization Song," telling of his arrival, their affair, and his departure. She has spent the past five in a futile search for her lover. She moves behind the wagon, and Courage warns her daughter against military affairs.
The Chaplain and Cook appear. Eilif has requested money; Courage gives some to the Chaplain, chiding her son for speculating in maternal love. The Cook says she is too hard: her son may die at any moment. The Chaplain rejoins that to fall in a war of religion is a blessing to his skeptical interlocutors.
The three move behind the cart, talking of politics. This campaign has cost the Swedish King a great deal. Neither the Poles nor Germans wanted their freedom from the Kaiser, forcing him to subjugate if not execute them. He got nothing but trouble for his outlays and so he had to levy an unpopular salt tax back home. In any case, his justification by God kept his conscience clear. Without it, he could be accused of seeking profit alone. Courage and the Chaplain chastise their friend for his disloyalty and he eats the king's bread. The Cook disagrees; he does not eat his bread, but instead bakes it.
While the three converse, Kattrin's dons Yvette's boots and imitates her sashay. Suddenly cannons, shots, and drums explode: the Catholics have launched a surprise attack. The Ordnance Officer and a Soldier enter and attempt to move the cannon. The Cook departs for the Commander, leaving his pipe behind. The Chaplain remains, wringing a cloak from the reluctant Courage to disguise himself. Discovering Kattrin, Courage rips off the boots and smears her face with dirt. When a clean face appears before a soldier, another whore comes into the world. To her horror, Swiss Cheese arrives and stupidly hides the regiment cash box in the wagon. They quickly take down the regiment flag.