Miskolc separated from Borsod County between 1907 and 1909. It became an independent municipality and an independent industrial trade, cultural and financial centre, the largest city of the region.

The preparation for World War I required an increase in the production of heavy industry (cannons, machine-guns and steel-bullets). Beside the factory of Diósgyőr, the ‘New Factory' was built for the sole purpose of producing munitions. The soldiers of the Miskolc Division fought in the Galician, Russian, Romanian, and Italian theatres of war. We still do not exactly know how many of them died on the different battlefields. In the cholera-infested barracks more than five thousand died out of the injured soldiers of World War I. The Cemetery of Heroes was opened at that time, where now many thousands of soldiers from more than ten nationalities rest. During the military events of Hungarian Soviet Republic, the dictatorship of the proletariat, the inhabitants of Miskolc had to endure first in May 1919 a Czech then in November a Rumanian occupation.

After the withdrawal of the Rumanian army, the Hungarian national army, the Horthy-infantry, marched in on 2 December 1919. Miklós Horthy, as the commander-in-chief, held a review on 19 December 1919 in Miskolc.

After the Peace Treaty of Trianon on 4 June 1920, when Hungary lost two-thirds of its lands, resettlements began. In the largest migration of the 20TH century many institutes had to be removed and people had to leave their homelands. Mainly the educated people wanted to join the mother country again. These people brought new energy and caused a significant change in the social face and intellectual life of Miskolc. It all happened when the trauma of Trianon shocked and paralyzed the country.

In 1919-1920 the population of the city increased from 51,000 to 57,000 and in 1930 they counted 62,000 people. The lost war, followed by the revolutions, the lost lands and the economic crisis disarranged the entire structure of Miskolc and changed the political and economic conditions that had been developing from the beginning of the century. As a result of the preparations for World War II, the city's industry grew and the situation got temporarily better until September 1939. Then a crowd of Polish refugees ‘exploded' into the society. From the autumn of 1939, during the German-Polish war, approximately 30-35,000 soldiers and civilians went across the county and Miskolc, recalling the horrors of World War I.

On 30 July 1941 the declaration of war against the Soviet Union was officially declared. That period was also heavily burdened with discriminative and inhuman laws against the Jews. Miskolc and Hungary were occupied by the German army on 19 March 1944. The war reached the eastern part of the country in the summer of 1944, and the city suffered an extremely heavy bomb attack on June 2ND. Flying from an Italian air base, almost a hundred aeroplanes took part in the attack in several waves, killing 206 people and injuring 420. Meanwhile, the concentration of the Jewish people from the county and the city into ghettos went on and from the factory of Diósgyőr they were deported to the concentration camp in Auschwitz. Between 12 and 15 June 1944, 15,464 people were carried away from Miskolc by three trains.

Miskolc and its surroundings became part of the operational area of combat from the beginning of November 1944. The defensive German troops left Miskolc and the Soviets could occupy the city without a battle.

During the Soviet occupation separate settlements around Miskolc were joined to the city by order (Ómassa, Újmassa, Lillafüred, Hámor, Diósgyőr, Pereces, Újdiósgyőr, Mindszent, Martin-kertváros (Martintelep), Szirma, Görömböly, Hejőcsaba, and Tapolca). The present border of Miskolc was formed at that time.