Although it had not participated in the attacks in April, Bulgaria occupied parts of both Yugoslavia and Greece shortly thereafter for the remainder of the war in the Balkans.

In this period the United Kingdom was supporting the Greeks with the Royal Air Force, but the arrival of British and Commonwealth ground troops in Greece was delayed due to operations in North Africa.

The invading Axis powers (Nazi Germany, Fascist Italy, and Hungary) occupied and dismembered the Kingdom of Yugoslavia.

Montenegro remained under Italian occupation, and Bulgaria was permitted to annex eastern areas of Yugoslavia, including most of modern-day North Macedonia.

Breaking through the Yugoslav lines in southern Yugoslavia allowed Germany to send reinforcements to the battlefields of northern Greece.

However, the heavy losses incurred by the paratroopers convinced the Supreme Command of the Wehrmacht to abandon large-scale airborne operations for the remainder of the war.

On 6 April 1941, despite having officially joined the Axis Powers, the Bulgarian government did not participate in the invasion of Yugoslavia and the Battle of Greece.

On 20 April, the Bulgarian Army occupied most of Western Thrace and the Greek province of Eastern Macedonia, which had been already conquered by Germany, with the goal of restoring its pre-World War I outlet to the Aegean Sea.

Throughout the remainder of the war, active Yugoslav, Greek, and Albanian resistance movements forced Germany and its allies to garrison hundreds of thousands of soldiers permanently in the three countries, denying them to the other fronts.

Especially in Yugoslavia after 1943, the threat of an Allied invasion and the activities of the partisans necessitated large-scale counter-insurgency operations, involving several divisions.