Following the 1938 annexation of Austria by Nazi Germany, Yugoslavia shared a border with the Third Reich and came under increasing pressure as her neighbours became aligned with the Axis powers.
In April 1939, Yugoslavia gained a second frontier with Italy when that country invaded and occupied neighbouring Albania.
At the outbreak of World War II, the Yugoslav government declared its neutrality.
Between September and November 1940, Hungary and Romania joined the Tripartite Pact, and Italy invaded Greece from Albania.
From that time, Yugoslavia was almost completely surrounded by the Axis powers and their satellites, and her neutral stance toward the war came under tremendous pressure.
In late February 1941, Bulgaria joined the Pact.
The next day, German troops entered Bulgaria from Romania, closing the ring around Yugoslavia.
With the aim of securing his southern flank for the pending attack on the Soviet Union, Adolf Hitler began placing heavy pressure on Yugoslavia to join the Axis powers.
The Yugoslav government conditionally signed the Pact after some delay, on 25 March 1941.
Two days later, a group of pro-Western Serb-nationalist air force officers deposed Prince Paul in a bloodless coup d'état.
The conspirators declared 17-year-old Prince Peter of age and brought to power a government of national unity led by General Dušan Simović.
The coup enraged Hitler, who declared: "even if Yugoslavia at first should give declarations of loyalty, she must be considered as a foe and therefore must be destroyed as quickly as possible."
He then ordered the invasion of Yugoslavia, which commenced on 6 April 1941.

Đujić did not support the coup, and was in Strmica with his family when the Axis invasion began.
He realised that Yugoslavia's collapse was inevitable after seeing a column of demoralised troops from the barely-mobilised 12th Infantry Division Jadranska pass his home.
Once it became clear that the Royal Yugoslav Army (Serbo-Croatian: Vojska Kraljevine Jugoslavije, VKJ) could not hold the Axis advance, Đujić started blaming Croat fifth column activity for the VKJ's military defeats.
On 10 April 1941, the Ustaše-led Independent State of Croatia (Croatian: Nezavisna Država Hrvatska, NDH) was proclaimed in Zagreb and divided into German and Italian zones of occupation.
The Italians divided those parts of the NDH that they occupied into three zones: Zone I was those parts of Dalmatia that were annexed by Italy and formed the Governorate of Dalmatia; Zone II was an area which was demilitarised in respect of NDH forces, but was under NDH civil administration; and Zone III was the remainder up to the demarcation line with the Germans.
This arrangement was implemented following the signing of the Treaties of Rome on 18 May. Following the signing, the Italians withdrew the bulk of their forces from Zones II and III, and those that remained there were formally considered to be allied forces stationed on NDH territory by mutual agreement.
Strmica and Knin were included in the NDH and fell within Zone II.
Following the 1938 annexation of Austria by Nazi Germany, Yugoslavia shared a border with the Third Reich and came under increasing pressure as her neighbours became aligned with the Axis powers. In April 1939, Yugoslavia gained a second frontier with Italy when that country invaded and occupied neighbouring Albania. At the outbreak of World War II, the Yugoslav government declared its neutrality. Between September and November 1940, Hungary and Romania joined the Tripartite Pact, and Italy invaded Greece from Albania. From that time, Yugoslavia was almost completely surrounded by the Axis powers and their satellites, and her neutral stance toward the war came under tremendous pressure. In late February 1941, Bulgaria joined the Pact. The next day, German troops entered Bulgaria from Romania, closing the ring around Yugoslavia. With the aim of securing his southern flank for the pending attack on the Soviet Union, Adolf Hitler began placing heavy pressure on Yugoslavia to join the Axis powers. The Yugoslav government conditionally signed the Pact after some delay, on 25 March 1941. Two days later, a group of pro-Western Serb-nationalist air force officers deposed Prince Paul in a bloodless coup d'état. The conspirators declared 17-year-old Prince Peter of age and brought to power a government of national unity led by General Dušan Simović. The coup enraged Hitler, who declared: "even if Yugoslavia at first should give declarations of loyalty, she must be considered as a foe and therefore must be destroyed as quickly as possible." He then ordered the invasion of Yugoslavia, which commenced on 6 April 1941.
Đujić did not support the coup, and was in Strmica with his family when the Axis invasion began. He realised that Yugoslavia's collapse was inevitable after seeing a column of demoralised troops from the barely-mobilised 12th Infantry Division Jadranska pass his home. Once it became clear that the Royal Yugoslav Army (Serbo-Croatian: Vojska Kraljevine Jugoslavije, VKJ) could not hold the Axis advance, Đujić started blaming Croat fifth column activity for the VKJ's military defeats. On 10 April 1941, the Ustaše-led Independent State of Croatia (Croatian: Nezavisna Država Hrvatska, NDH) was proclaimed in Zagreb and divided into German and Italian zones of occupation. The Italians divided those parts of the NDH that they occupied into three zones: Zone I was those parts of Dalmatia that were annexed by Italy and formed the Governorate of Dalmatia; Zone II was an area which was demilitarised in respect of NDH forces, but was under NDH civil administration; and Zone III was the remainder up to the demarcation line with the Germans. This arrangement was implemented following the signing of the Treaties of Rome on 18 May. Following the signing, the Italians withdrew the bulk of their forces from Zones II and III, and those that remained there were formally considered to be allied forces stationed on NDH territory by mutual agreement. Strmica and Knin were included in the NDH and fell within Zone II.
Momčilo Đujić