Template:WarInfobox (BGA) Following Austria-Hungary's defeat and collapse after WW1, the new Kingdom of Hungary was drawn into a war. The Triple Entente demanded Hungary cede much of its territory to neighbouring nations. Hungary refused these demands and was drawn into war with Romania, Serbia, and Bohemia.
Following the collapse of Austria-Hungary political turmoil in Hungary ensued. It was unclear on who would lead the new nation. Istvan Tisza took power and promised to work with the allied powers to ensure Hungary's future. Istvan advocated for Hungary's borders to remain the same with minor revisions and plebiscites. However the allied powers did not share this same ideas. Romania was already occupying much of Transylvania and Bohemia had taken most of Slovakia. Croatia had declared independence while Serbian troops seized Banat. Istvan wanted to come to a peaceful solution. After a meeting with the leader of Romania, it was clear that Romania would not pull out of Transylvania.
Croatia to the south decided to reject Serbia's offer to join Yugoslavia. Serbia responded by declaring war on Croatia and invading the nation. Now Croatia was stuck between Serbian oppression or to look for help. Italy was eyeing Croatia's coastline and would not aid. Similarly, the Entente favored a Yugoslavian state over separate Serbian and Croatian ones. Croatian leader, Stjepan Radic, faced with no more options, asked Hungary for aid. Istvan accepted this invitation and Hungary went off to war.
Hungary was faced with three fronts and limited allies. Croatia's army was made up of mostly militia and was facing an organised Serbian force. Hungary however had a strong and somewhat organised force. War was officially declared in November 1918 against Bohemia, Romania, and Serbia. Romania made the first move by cutting off the Hungarian holdout of Szekely Land from the rest of Hungary. With Szekely cut off, Romania launched an assault aimed to bring down the holdout region. The ethnic Hungarian population of Szekely fought with anything, many with old rifles and crossbows. In the end the Romanians won but it cost them many more casualties than anticipated and delayed their planned attack of the new defence line being created by Hungarian troops.
Istvan realised he needed to lessen the amount of enemies Hungary was facing. He chose to knock out Bohemia. He launched an attack at the inexperienced Bohemian army and recaptured most of Slovakia. Hungary achieved a major victory in Bratislava and pushed the Bohemian and Slovak forces to the border. Then the leader of Bohemia decided to sign peace with Hungary. The treaty recognised Hungarian sovereignty over Slovakia. This however resulted in Romania being able to breach Hungarian defences and advancing into Transylvania further.
The Siege of Belgrade
Serbian forces managed to crush the Croatian military in Split. The demoralised Croatian army began to think it was impossible to defeat the Serbians. As Serbia began putting pressure on Zagreb, the Hungarian military arrived and quickly defeated the Serbians. During the chaos, Italian troops seized the major port city of Split and the Dalmatian Islands. With Serbia running out of Croatian territory, the Hungarians began the siege of Belgrade in an attempt to force a Serbian armistice. Using new tactics and most importantly, planes, the Hungarians triumphed and captured the city. Serbia agreed to an armistice and Hungarian troops were quickly moved to halt the quickly advancing Romanian army. Serbia signed an official peace treaty two months later.
After the armistice with Serbia, Istvan and Stjepan sat down to discuss the future of Croatia. Croatia had effectively no military left and needed Hungary's protection. Istvan proposed Croatia rejoined Hungary but remained autonomous to a great extent. Stjepan decided to chose autonomy over oppression. The reunion was gloriously proclaimed on May 7th 1919.
Liberation of Transylvania
The advancing Romanian army seemed to be unstoppable. The Hungarian army and Romanian army clashed in Debrecen to decide who would win the war. The fighting was bloody and ruthless. In the end, Hungary triumphed and cost the Romanians thousands of soldiers. Hungary charged into Transylvania, beating several attempted Romanian offensives and defensives. By November 1919, Hungary had reached Szekely Land. However Romanian reinforcements arrived and the war began to descend into one of attrition. Both nations knew they would be unable to support such a war and looked to settle peace.
The Peace Treaty
Poland agreed to head the peace conference between Hungary and Romania. Hungary demanded to be able to retain all of Transylvania. After several days of debate an armistice was agreed upon. During the conference, Istvan was assassinated by a Romanian spy. This sparked internal division and chaos in Hungary which the Romanians wanted to take advantage of. Unfortunately for them, Karl Hapsburg arrived an retook the throne, preventing a fallout in Hungary. France supported Karl's ascension and pushed for a peace treaty.
Three months after the armistice, Romania launched a surprise offensive and briefly occupied portions of southern Transylvania. Hungary managed to push them out in a costly two-month longcampaign. Finally Romania agreed to peace, however Romania's major demand was that the Romanian minority was to be given a guarantee of their rights. The treaty was finalized on May 7th 2020.