Prior to that, he was a leader of the Protestant faction in Hungary and a faithful supporter of Gabriel Bethlen, his predecessor as Prince.

When Bohemian nobles requested military support in their struggles against the Habsburg monarchy, Rákóczi persuaded Bethlen to help and commanded Transylvanian forces in several battles.

[1] Sigismund, who was a successful military commander in Royal Hungary, was the first member of the Rákóczi family to rise to prominence.

[6] Through sending George to Kassa, Sigismund demonstrated his support to Bocskai[5] who made him the governor of the Principality of Transylvania in September 1605.

[7] Although Sigismund lost the throne, his short reign in Transylvania strengthened his sons' position, because no other noblemen could demonstrate a princely origin.

[4][9] Bálint Drugeth (who was the husband of their eldest sister), their father's widow, Borbála Telegdy, and her son-in-law, István Kendi, sued them for parts of their inheritance.

[21][26] A day later, his Hajdú troops tortured and murdered three Jesuit priests, Melchior Grodziecki, Marko Krizin and Stephen Pongracz.

[28] Drugeth hired irregular troops (primarily Cossacks) in Poland and broke into Zemplén County on 21 November.

[34] However, Ferdinand's troops inflicted a decisive defeat on the Bohemian army in the Battle of White Mountain on 8 November.

[35] His commander, Bucquoy, invaded Upper Hungary, forcing Bethlen to withdraw his troops as far as Kassa in the first half of 1621.

[37] After Bethlen's opponents seized the fortress of Fülek (now Fiľakovo in Slovakia), Rákóczi laid siege to it in April, but he could not force the defenders to surrender.

[41] The Peace of Nikolsburg authorized Bethlen to rule seven counties in Hungary—Abaúj, Bereg, Borsod, Szabolcs, Szatmár, Ugocsa and Zemplén—till the end of his life.

He sent his men to Silesia and Poland for mercenaries, called the Transylvanian Hungarian nobility, the Székelys and the Hajduks to war.

[43] In response, Sultan Murad IV sent 20-30 thousand Turkish soldiers against Transylvania led by Bekir Bey.However, the Ottoman troops were defeated by the Transylvanian forces at Szalonta on 6 October,[44] and Husein Pasha when he heard this he realized that that he is forced to make peace with Rákóczi.

According to the Treaty of Szászváros, the sultan recognizes Rákóczi's full authority over Transylvania, and he grants amnesty to Bethlen.

Due to the failure of the campaign, the Sultan killed Begir Bey and replaced the Pasha of Buda, Husein.

George Rákóczi immediately sent his general János Kemény with a few thousand Székely infantry and cavalry, to help Matei.

[47][48] In November Kemény's brigade crossed the Eastern Carpathians and united with Matei's forces and together they pushed Lupu back to Moldavia.

[49] However, the Moldavian ruler did not give up and attacked again two years later, but Matei defeated him again with the help of a Transylvanian cavalry team sent by Rákóczi near Bucharest on 6 December 1639.

Rákóczi made a tactical retreat to the south and left his faithful man Reöthy Orbán with 3,000 men in Kassa.

Götz was forced to retreat from Kassa after an 11-day siege, however Kemény was on their trail and, attacking their rearguard at Somos on 26 June, thoroughly routed it.

Despite this, Rákóczi continued his campaign and in June crossed the Moravian border, personally joined the Swedish army besieging Brno for a projected march against Vienna.