A guerrilla resistance leader battles Nazi troops in German-occupied Yugoslavia.

After the Germans overrun Yugoslavia in 1941, Serbian army colonel Draja Mihailovitch leads a small but fierce band of guerrillas known as the Chetniks. Mihailovitch's men succeed in wreaking havoc on the German forces, which have been joined by their Italian allies, and force seven divisions of the enemy to combat the Chetniks instead of fighting at the front. One day, the Chetniks capture an Italian supply convoy, and Mihailovitch radios German headquarters in the nearby town of Kotor and impudently offers to exchange his Italian prisoners for gasoline. Infuriated, General Von Bauer refuses, but when Mihailovitch threatens to notify the Italian High Command of his decision, Gestapo colonel Wilhelm Brockner orders Von Bauer to comply. Brockner, who has been frustrated in his attempts to find Mihailovitch, is convinced that the Yugoslavian leader's wife Lubitca and their two children, Nada and Mirko, are hiding in Kotor, and that he can use them to obtain Mihailovitch's surrender. Brockner warns the townspeople that anyone caught aiding the Mihailovitch family will be executed, and prepares for the transport of two thousand men from Kotor to Germany. Unknown to Brockner, his secretary Natalia is a spy for the Chetniks and is the sweetheart of Alexa, one of Mihailovitch's aides. Armed with Natalia's information, the Chetniks attack the train transporting the two thousand prisoners and free them. In retaliation, Brockner decrees that no food will be distributed to the citizens of Kotor until Lubitca and her children are turned over to the Germans. Lubitca tries to surrender to Brockner but is stopped by Natalia, after which Mihailovitch asks to meet with Von Bauer and Brockner. When Mihailovitch arrives at German headquarters, however, Von Bauer declares that, because the official Yugoslavian government capitulated to the Germans, international law does not prevent him from killing Mihailovitch, even though they are meeting under a flag of truce. Mihailovitch calmly informs the general that the Chetniks are holding his wife and daughter as hostages, as well as Brockner's mistress, and that they will be killed if the citizens of Kotor are not fed. The general angrily releases Mihailovitch and provides rations for Kotor, but regains the upper hand when Mirko's patriotism betrays his true identity to his German schoolteacher. After taking Mirko into custody, Von Bauer and Brockner escort Lubitca to Mihailovitch's mountain stronghold and there inform him that every man, woman and child in Kotor will be executed unless the Chetniks surrender within eighteen hours. After Mihailovitch sadly tells Lubitca that he cannot submit, she returns to Kotor to comfort their children. Mihailovitch immediately organizes a plan of attack and sends some of his men to the mountain pass to Kotor, where they will trick the Germans into thinking that they are surrendering, while the rest of the Chetniks attack the town via the mountains on the other side. Despite the capture of Alexa, who was assigned to infiltrate the German artillery, Mihailovitch's plan succeeds. After a bloody battle, the Chetniks gain control of Kotor and free all of the hostages, including Mihailovitch's family. Soon after, Mihailovitch broadcasts a radio message to his fellow Yugoslavs that the guerrillas will continue to fight until they have regained complete freedom for their people.