Given the task definition and input, reply with output. In this task, you will be shown an extract from a movie plot and a question. You need to provide the correct answer for it. Short answers containing words that are present in the passage are preferred.

On Sunday, April 6, 1941, German troops and tanks invade Yugoslavia while the capital Belgrade is bombed. After the Yugoslavian government surrenders, Yugoslav Army Colonel Draza Mihailovich leads a group of guerrillas known as the Yugoslav Army in the Homeland, or Chetniks, who launch a resistance movement against the Axis occupation. The guerrillas tie up seven Axis divisions that are pitted against them.In the first guerrilla operation, the Chetniks seize an Italian supply convoy. They exchange the Italian prisoners for gasoline. Gestapo Colonel Wilhelm Brockner is humiliated. He seeks to capture Mihailovich. German Wehrmacht General Von Bauer sends his troops against Mihailovich but is unsuccessfulBrockner plans to capture Mihailovich's wife Ljubica and their two children, Nada and Mirko, who are living under assumed names in Kotor in Montenegro. He will then force Mihailovich to surrender to save their lives. Anyone who helps them will be shot.Brockner's secretary Natalia, a spy for the Chetniks, informs them that 2,000 Yugoslav prisoners will be transported by rail to Germany. The Chetniks ambush the train and enable the prisoners to escape.Brockner next orders that the people of Kotor will be starved until they turn in Mihailovich's wife and children.Mihailovich negotiates a meeting with Brockner and Von Bauer. This is a trap. Von Bauer informs Mihailovich that he will be executed because under international law he is not a legal combatant. Mihailovich informs him that his forces have captured his wife and daughter. Von Bauer is forced to release Mihailovich. The people of Kotor receive food again.Mirko, Mihailovich's son, exposes his identity to the German schoolteacher. She informs Brockner. Mihailovich's wife and children are taken hostage. The decree is issued that every man, woman, and child in Kotor will be executed unless the Chetniks surrender within 18 hours. The Chetniks deceive the Germans into thinking that they are surrendering, while the rest of the Chetniks attack the town from the mountains on the other side.After a climactic battle, the Chetniks gain control of Kotor and free all of the hostages, Mihailovich's family, and Aleksa, the Chetnik commander.In the final scene, Mihailovich broadcasts a radio message to the people of the former Yugoslavia that the guerrillas will continue fighting until they have regained complete freedom and driven out the invading Axis troops., Question: Where do German troops and tanks invade on Sunday, April 6, 1941?

Answer: Yugoslavia