The fourth act begins outside the enemy city of Arras (in Northern France), still in the year 1640. The cadets sit huddled around a fire. Captain Carbon and Le Bret keep watch while Christian sleeps alongside his peers. Le Bret tells Carbon that there is a famine in the camp. As they talk, they hear someone approaching—it is Cyrano de Bergerac. Cyrano has just come from delivering his latest letter to Roxane. Cyrano explains to Le Bret that Roxane has instructed Cyrano to make sure that “Christian” writes often to her—as a result, Cyrano sends a new letter every day at dawn. Le Bret admires Cyrano for his bravery (he must put himself in danger to deliver the letters), and notes, sadly, that Roxane must never know that her beloved Christian is slowly dying of starvation as the siege of Arras goes on. In response, Cyrano simply says that he needs to get to work writing tomorrow’s letter—with this, he goes into his tent.
After the madcap comedy of Act 3, it now comes as a shock to see the miserable state of the French army. Christian and Cyrano are both suffering on account of de Guiche’s spiteful revenge and the harsh realities of war. And yet Cyrano, who’s committed to keeping Roxane’s love as pure and untainted as possible, doesn’t say anything in his letter about the famine in the French camps. Cyrano is faithfully keeping his promise to protect Christian and make sure he writes, but of course Cyrano is also writing because he wants to—because writing to Roxane is the only channel through which he can express his feelings for her.