Rubuta ci gaba don wannan sakin layi - Don cin gajiyar sha'awar Ferdinand game da Tawayen Bohemia a farkon Yaƙin Shekaru talatin, Bethlen ya mamaye Habsburg-wanda ke kula da Royal Hungary a 1618 kuma ya ci gaba da cin nasara har zuwa 1620. Kodayake an sasanta zaman lafiya a watan Janairun 1620 yana ba Bethlen larduna 13 a gabashin Royal Hungary, yariman ya ci gaba da yaƙin a watan Satumba. Rawar da Ferdinand ya yi wa mutanen Bohemia a Yaƙin White Mountain
a watan Nuwamba ya ba shi damar mayar da hankali ga sojojinsa a Bethlen, kuma sarkin ya iya sake cinye mafi yawan Royal Hungary ta 1621. Domin Bethlen bai rarraba dukiyar da aka kwace daga manyan Katolika ga manyan Furotesta kamar yadda ya yi alkawari ba, sun janye goyon bayansu. Wadannan matsaloli, da kuma rashin goyon bayan Bethlen daga Daular Ottoman, ya jagoranci Bethlen da Ferdinand don neman sharuddan a Nikolsburg.