Franz Graf Thun-Hohenstein was born at Choltic (Bohemia) on the 27th of July 1826. He entered military service on the 11th of April 1844 as cadet in infantry regiment number 28 shortly followed by his promotion to Leutnant. He was then transferred to infantry regiment number 1 where he received his promotions to Oberleutnant and Hauptmann. With this regiment he took part in the revolutionary war of 1848 and 1849. In 1848 he saw action in the street fighting at Milan on the 18th to the 22nd of March, during the battle near Morazzone on the 26th of August and during the siege and capture of Vienna between the 23rd and the 28th of October. For his performance at Milan he received a public commendation and for his heroic acts during the attack on Vienna he was honored with the award of the Military Merit Cross. During the year 1849 he took part in the storming of Cava on the 20th of March, the battle near Mortara on the 21st of March where he received some wounds, in the battle of Novara on the 23rd of March where he was wounded again and in the assaults on Livorno on the 10th and the 11th of May were he especially distinguished himself during the capture of the suburb of St-Lucia. For all this actions Graf Thun was honored with public commendations by the army headquarters. After the war, meanwhile promoted to Major, Graf Thun was transferred to infantry regiment number 49 and permanently attached to Feldmarschall Radetzky, first as his Ordonannz-officer and later as his Flügeladjutant (personal adjutant).
When the famous field marshal died in 1857 Major Franz Graf Thun was transferred back to his regiment where he was appointed commander of the Grenadier battalion in April 1859. With this battalion of infantry regiment number 49 he took part in the war of 1859 in which he was honored with the commendation of the Kaiser for his performance during the battle of Solferino on the 24th of June where he was wounded again and the knight's cross of the Order of Leopold with war decoration for his performance during the battle of Montebello on the 20th of May - award date was the 7th of June 1859. Following the death in action of the commander of infantry regiment number 9 during the battle of Montebello, Graf Thun was transferred to this regiment as the interim commander and promoted to Oberstleutnant on the 1st of July 1859, shortly followed by his promotion to Oberst on the 13th of July 1859.
When the Austrian Volunteer Corps was raised Erzherzog Maximilian looked for a skillful and experienced commander and offered this post to Oberst Graf Thun. Since the 1st of April 1864 a commission under the chairmanship of Feldmarschall-Leutnant Adolf Freiherr Schiller von Herdern worked on the project "Volunteer Corps" while Generalmajor Ritter von Uieyski and Wilhelm La Vigne were the temporary garrison commanders of the corps at Laibach. On the 20th of August 1864 Kaiser Franz Joseph allowed him to enter Mexican service as a General and commander of the Austrian Volunteer Corps (his promotion-commission dated the 15th of August 1864) and Franz Graf Thun took over completely responsibility of the corps from the previously named generals. During the following years, he established his headquarters at Puebla, his main efforts were to keep the Austrian Volunteer Corps as an independent unit and to avoid any subordination to foreign command which lead to permanent troubles with the French headquarters, especially Marshal Bazaine, and not least with Emperor Maximilian. The Emperor always dreamed of a Mexican national army and so he desired the disbanding of the different foreign legions and their complete amalgamation with the regular army. It seems that this glowing conflict between him and the Emperor resulted in him receiving fewer and lower grade decorations than for instance Oberst Van der Smissen, the commander of the smaller Belgian Volunteer corps! When the foreign legions were disbanded following international criticism especially form the USA on the 6th of December 1866, Graf Thun refused to join the national Mexican army and traveled back to Europe. In Mexico he was honored with the award of the Bronze Military Merit Medal and the grand officer's cross (commander's cross with breast star) of the Order of our beloved Madonna of Guadalupe, back in Austria he was honored by Kaiser Franz Joseph with the award of the 2nd class of the Order of the Iron Crown with war decoration.
On the 14th of February 1867 he was recalled to full duty in the Austro-Hungarian army by receiving his promotion to Generalmajor and the appointment as a brigade commander in the 13th infantry division, followed by his transfer in the same capacity to the 8th infantry division at Innsbruck in December 1867. On the 27th of April 1871 he was transferred as commander from Innsbruck to the brigade at Trient. On the 28th of December 1871 he took over command of the 25th infantry division. During the year of 1872 he was honored with the award of the commander's cross 1st class of the Saxon Order of Albrecht and the commander's cross with breast star of the House order of the Wendischen Crown from Mecklenburg. Graf Thun received his promotion to Feldmarschall-Leutnant on the 24th of April 1873 and was appointed commander of the 8th infantry division at Innsbruck in January 1874, being now military commander of his beloved second homeland, the Tyrol. On the 16th of June 1877 he married there Auguste-Eugenie Princess von Urach (Stuttgart, 27th December 1842 - Schwaz, 11th March 1916) making Schwaz near Innsbruck to his final home. In December 1882 he took over command of the 14th Corps at Innsbruck, shortly followed by his promotion to Feldzeugmeister, becoming additionally Landesverteidigungs Kommandant für Tirol und Voralberg (Territorial Defence Commander). For his skillful support of the civil authorities during the flood disaster in winter 1882/83 he again received the commendation of the Kaiser Franz Joseph on the 1st of February 1883. However at this time his health began to worsen so that in December 1883 he was relieved of his post on health grounds and on the 10th of December he was placed on half-pay status, additionally honored by the award of the 1st class of the Order of the Iron Crown (with war decoration of the 2nd class) for his long years of excellent service. Finally his worsening health precluded his return to active duty and so he was permanently retired on the 1st of January 1887. Feldzeugmeister Franz Graf Thun-Hohenstein died at Schwaz on the 30th of July 1888.