A revolution broke out in Russia in March 1917. Mannerheim, who had been Commander of the army corps in Rumania but had been injured in an accident and hospitalised, came in September that year to the conclusion that he could not serve in an army which was drifting towards anarchy. In December 1917 he went by train from Odessa via St. Petersburg to Finland, making a very dangerous journey through a disordered Russia.
Finland had made a declaration of independence on December 6, 1917. However, circumstances were very unstable, as there were 40,000-100,000 Russian soldiers in Finland and an armed confrontation between the Red Guards founded after the March revolution in Russia and the Civil Guards seemed inevitable. To establish order in the country, the Senate on January 15, 1918, authorised Lieutenant-General Gustaf Mannerheim to form Government troops in north Finland and to act as their leader. The Civil Guards were appointed Government troops.
In order to form a support area, the Civil Guards disarmed the Russian troops in a surprise attack in Ostrobothnia. The Finnish Civil War had begun. The Red Guards took control of south Finland. Armed fights between the legal Government troops, that is the White Guards, and the Red Guards started at the end of January. The war of independence turned increasingly into a civil war. Mannerheim, Commander-in-Chief of the White Guards, first led operations from his headquarters in Vaasa. In early February head quarters were transferred to a train placed in the Seinäjoki railway yard. Towards the end of the war the headquarters were placed in Mikkeli. In addition to the Civil Guards, the Government troops consisted mainly of troops liable for military service. There were very few officers at first, but the situation improved significantly at the end of February, when more than 1200 Jägers, which had trained in Germany for Finland's War of Independence, returned to Finland.
Mannerheim, who had been promoted to General of Cavalry in March, rapidly obtained absolute authority in the Government troops. His assessed situations coolly and carried out operations decisively. He would have liked to liberate Finland with Finnish troops only, but the Senate also called in German troops to the War of Independence. They contributed to the rapid ending of the war but did not decide it. The last victorious battles of the Government troops took place in Vyborg and South Häme at the turn of the month April-May 1918. On May 16 a big victory parade was arranged in Helsinki. "The White General" Mannerheim rode at the head of his troops. The War of Independence was over. The Russian revolution did not spread to Finland and Finland's independence was secured.
After the War of Independence, Mannerheim proposed that a large number of the imprisoned Red Guards should be freed and that prisoners on the whole should be better treated. He did not agree with the Senate in questions concerning foreign policy and the future arrangement of the army. Mannerheim resigned from his office as Commander-in-Chief and left the country at the end of May 1918, first for Sweden and then for France and England.
Opinions diverged very much as to Finland's future form of government. While waiting for the situation to clarify, the Parliament, after voting in December 1918, nominated Mannerheim Regent of Finland. In this office Mannerheim signed Finland's republic form of government on July 17, 1919. In the presidential election carried out by the Parliament, Mannerheim lost to K.J. Ståhlberg, President of the Supreme Administrative Court, and on his own volition withdrew from Finnish state affairs for twelve years.
Mannerheim's position changed radically in 1931. He was then nominated Chairman of the Defence Council. The Council did not have independent executive authority. However, his personal authority made Mannerheim a very significant factor in Finnish politics. As Chairman of the Defence Council he particularly wished to increase the acquisition of armaments. This grew in importance from year to year, as the situation in Europe got more strained. However, the Parliament did not grant the necessary appropriation in time. Mannerheim, promoted to Field Marshal in 1933, also made inspection trips in Finland and visited other countries in order to study the political and military developments.
When World War II broke out in September 1939 and the Soviet Union made territorial claims on Finland, Mannerheim wished to make certain concessions in order to avoid a war, in which he saw no chances for Finland to be successful. He well knew the situation of the defensive forces and their grave lack of materials.
The Soviet Union launched an attack on Finland on November 30, 1939. The Finnish Winter War had begun. President Kyösti Kallio handed over the office of Commander-in-Chief to Field Marshal Mannerheim, who was then 72 years old. Throughout the war the Commander-in-Chief had his headquarters in Mikkeli. Right from the start of the war, Mannerheim's authority in all public circles was a very important element in strengthening the whole nation's will to defend its country. The nation, divided by the 1918 events, finally united in the Winter War. Irrespective of their political views, the Finns trusted Mannerheim.
As Chairman of the Defence Council Mannerheim had entered deeply into Finland's defence plans. However, the number of Russian troops, particularly between Lake Ladoga and the Arctic Ocean, was a surprise to the Finns. The Commander-in-Chief had to make very difficult decisions with a view to the allocation of the small number of Finnish troops. On the Karelian Isthmus the enemy could, up to mid February 1940, be repelled at a position given the name of "the Mannerheim line". It was not a solid fortified position; the line consisted of soldiers fighting bravely in defective positions.
Towards the end of the Winter War, when the enemy's superior force was beginning to be overpowering, Mannerheim recommended the conclusion of an armistice with the Soviet Union. The Winter War ended on March 13, 1940. Moscow's peace terms were very heavy, but honourable from Finland's point of view. This was the result of the tenacious fighting of the Finnish soldiers. They were led by their Commander-in-Chief, Field Marshal Mannerheim. In the 105 glorious days of the Winter War, the Soviet Union was unable to crush the Finnish army. It was "the Wonder of the Winter War".
When Germany attacked the Soviet Union on June 22, 1941, Finland declared itself neutral. However, Soviet airplanes heavily bombed targets in Finnish territory and so, on June 25, Finland found itself at war with the Soviet Union. The Continuation War had begun. Commander-in-Chief was once again Field Marshal Mannerheim. Finland's military objective was to recover the territories lost in the Winter War and to occupy the lake isthmuses, which were easy to defend. The wrong of the Winter War was to be corrected. The Finns achieved their objective in early December 1941, when offensive operations ended and positional warfare began.
The Finns did not attack Leningrad or the Murmansk railway line. This was the very clever decision of Commander-in-Chief Mannerheim. He held a very central position, not only in leading Finnish operations but also in making foreign policy decisions. He was one of the four or five people who led Finland throughout the war.
Mannerheim celebrated his 75th birthday on June 4, 1942. As a present, the Government awarded him the title of Marshal of Finland. Another mark of respect is that since 1943, Mannerheim's birthday has been celebrated as the flag day of the armed forces. The Commander-in-Chief also received numerous presents from his soldiers. The best-known present is the hunting cabin given by the 14th Division, which had fought in the Rukajärvi area. A congratulatory visit from Reichskansler Adolf Hitler himself was a real surprise. The Commander-in-Chief met his guest with cold civility.
In June 1944 the Soviet Union launched a massive attack on the Karelian Isthmus. The attack resulted in a breakthrough. After ten days of delaying actions and retreat, Commander-in-Chief Mannerheim sent the troops an appeal to put a stop to the enemy's invasion and start a rigid defensive warfare. The weighty appeal and the transferring of troops from eastern Karelia to the Karelian Isthmus were effective. After very heavy fighting, the Soviet attack ended in a Finnish defensive victory by mid July.
In accordance with the preconditions of the armistice, Finland was obliged to turn its weapons against its former brother-in-arms, Germany. The Germans had defended north Finland during the Continuation War and did not without fighting leave Finland within the time fixed. Mannerheim's absolute authority made it possible, in a changed situation, to carry out the ungrateful but inevitable operations against the Germans as demanded in the terms of armistice. With the exception of a very small region in northwest Lapland, the Germans had left Finland by the beginning of December 1944, and by April 27, 1945, they had retreated completely. The war was over.
Having repelled the Soviet attack in summer 1944, Finland had a much better chance of concluding armistice with the Soviet Union on tolerable terms. What was needed now was a person capable of disengaging Finland from the war. President Risto Ryti resigned and Parliament elected Mannerheim President by virtue of an emergency law. He was inaugurated on August 4, 1944. His authority and judgement contributed significantly towards the armistice taking effect on September 4, 1944. Finland retained independence without being occupied. The defensive victory of summer 1944 decided Finland's fate.
During Interim Peace in 1940 a new, very prestigious decoration, the Mannerheim Cross of the Cross of Liberty, was founded. It could be awarded a particularly brave or deserving soldier irrespective of his military rank. In this respect it differed from other decorations. Only 191 soldiers were nominated Knights of the Mannerheim Cross, their military ranks varying from private to field marshal. Four soldiers were awarded the Mannerheim Cross twice.