Paul Bernnart was born on the 18th of February 1828 in Vienna as the son of a civilian official. In some sources his family name was spelt "Bernart" or "Bernhart" but in his military files and in the Schematismus he is written as "nn". After successfully attending the Gymnasium of the Löwenburg Convent he entered military service as a common soldier in infantry regiment number 49 on the 7th of October 1845. After his promotion to Unterleutnant 2nd class on the 17th of August 1848 he was employed as a battalion adjutant followed by his promotion to Unterleutnant 1st class on the 20th of June 1849. During the war of 1848 he took part in the blockade of Istria but did not see any action. During 1849 he took part in the skirmish at Poroszlo on the 18th of March, the engagements at Katvon on the 2nd of April and Tapio-Büske on the 4th of April, the battle at Izsaszeg near Gödöllö on the 6th of April and in addition in the several actions at Rakos on the 10th, the 11th, the 13th, the 16th and the 21st of April. He also took part in the encounters at Szigetvar on the 5th of May, at Hochstrass on the 12th and the 19th of May, at Raab on the 28th of June as well as in the advance guard engagements near Aranyos and Szent Paul-Puszta on the 1st of July. During the battle of Komorn on the 2nd of July he was wounded by a grazing shot to his left arm in the forest of Acser. Bernnart remained with his regiment but during the next battle of Komorn on the 11th of July he was seriously wounded in the right foot and in the right thigh. For his dashing performance during this battle he received the commendation by the Kaiser on the 1st of September 1849 and for his excellent contribution during the whole campaign of 1849 he was honored with the award of the Military Merit Cross on the 31st of January 1850, which allowed him to wear this decoration with the war decoration when this was introduced ten years later.
On the 15th of October 1852 Leutnant Bernnart was transferred to infantry regiment number 45 at Verona. There he was engaged to reorganize the Landwehr-Battalion at Mauer near Vienna until his promotion to Oberleutnant on the 1st of December 1853. From 1855 to 1860 he was engaged as an Aide de Camp to the owner of his regiment, Feldmarschall-Leutnant Erzherzog Sigismund, first at brigade then at division level. Meanwhile he received his promotions to Hauptmann 2nd class on the 13th of April 1859, shortly followed by the promotion to Hauptmann 1st class on the 26th of May 1859. During the battle of Magenta on the 4th of June 1859 Hauptmann Bernnart was seriously wounded by a shot through his left upper arm. For his heroic performance during this battle he again received the commendation of the Kaiser on the 27th of June 1859. His personal relationship to Graf Thun-Hohenstein made it possible that he entered Mexican military service as one of the first officers on the 31st of July 1864 as Hauptmann 1st class in the Jäger and there he helped to organize the troops. With the first ship, the "Bolivian" he left Trieste on the 18th of November 1864 and in Mexico he took over command of the 1st battalion followed by his promotion to Major with seniority of the 31st of May 1865.
As commander Paul Bernnart lead his troops through the first expedition into the Sierra del Norte and heroically took part in the battles at Zacopoaxtla on the 12th of April, at Xochiapuelo on the 13th of April and at Huahuastla on the 21st of April 1865. For his efforts in building and leading the troops he received the commendation of General Graf Thun on the 24th of April 1865 and for his performance during battle he was honored with the award of the knight's cross of the Order of our beloved Madonna of Guadelupe on the 17th of May 1865. Major Bernnart was a calm, prudent officer who thought twice before acting and consequently it was no wonder that the young, ambitious adventurers like Kodolitsch or Khevenhüller had their problems with him - like fire and ice. General Graf Thun preferred his deliberate style but he was often criticized by younger officers because he prefered to save his troops before an attack before a possible chance for a victory. From July to December 1865 he was district commander at Jalapa and then in the same position at Puebla until June 1866. In June 1866 Major Bernnart was attached to the war ministry and became district commander of Mexico City. At this time it was obvious that the Mexican adventure was doomed, and for more than 2 months the Volunteer Corps had not received any payment and the offer to enter the Mexican National Army was widely ignored. Khevenhüller noted in his diary that only those desperadoes who had no chance to be welcomed back in Europe had enlisted in the Mexican army, the majority wanted to return to Austria. The agreement between the Austrian and the Mexican government stated that those who had left the Austrian army could return after 6 years of service with the Volunteer Corps but now only 2 years had passed and so some officers including Major Bernnart petitioned General Graf Thun asking him if he had any influence to manage an earlier return to the Austrian army for them. The commander of the Volunteer Corps realized that such an action would immediately lead to a breakdown of his troops and sharply refused to accede to this petition. Consequently Major Bernnart was removed from his important post in the capital city and transferred to Huajuapan as district commander in August 1866 where he commanded the troops during the expedition against Oajacca from the 19th and 20th of September 1866. At the end of October 1866 Major Bernnart was also relieved from his post at Huajuapan. In December 1866 he left Mexico and was again assigned to infantry regiment number 45 as an Hauptmann 1st class on the 7th of April 1867.
On the 1st of February 1868 he was transferred to infantry regiment number 18 at Josephstadt first as a company commander and then from the 1st of May onward as commander of the 5th battalion. On the 1st of November 1870 Paul Bernnart was promoted to Major, with seniority of the 8th of November, with additional transfer to infantry regiment number 31 at Fiume. Major Bernnart's personal files state that he spoke German, French, Italian and Spanish well and also a little Polish but he was not able to master the examinations for the Hungarian language which was the regimental language of IR 31 and so he was transferred on the 1st of May 1872 to the Trieste infantry regiment number 22 at Ragusa. In April 1873 he was appointed provisional commander of the newly formed Landesschützen battalion "Roveredo" number 9. On the 2nd of April 1874 he was honored with the award of the officer's cross of the Italian Order of the Crown. In the same year he married and they had a son but his military files did not give the birthdates or names - neither of his wife nor of his son. On the 17th of August 1874 Major Bernnart was transferred to the k.k. Landwehr definitively appointed commander of his independent Landesschützen battalion. After his promotion to Oberstleutnant on the 1st of May 1876 he assumed command of Landwehr infantry battalion "Pilsen" number 35 on the 30th of October 1876. At Pilsen he received his promotion to Oberst on the 25th of October 1878 and nearly a year later, on the 23rd of October 1879, he took over command of Landwehr battalion "Triest" number 72. In September 1882 Oberst Bernnart was transferred from the Landwehr back to the k.u.k. Army becoming commander of his old regiment, infantry regiment number 45 on the 6th of September 1882. Only two and a half year later, in March 1885, he was appointed commander of the 31st infantry brigade at Kronstadt (Siebenbürgen) where he received his promotion to Generalmajor on the 1st of November 1885 with seniority of the 28th of October.
Paul Bernnart's annual confidential reports were always excellent but from the year 1886 onwards his superior commanders started to worry about his age, expressing their opinion that he reached his ceiling - so it was obviously clear that he would never get the command of a division. On the 27th of February 1887 Generalmajor Bernnart took over command of the 19th infantry brigade at Josephstadt. As it was a command on the same level he must have realized at this time that his possibilities for further promotions and/or the command of a division were gone. With regardto the imperial order of 1873 the time in the Mexican Volunteer Corps was deducted from the service years required for the pension and also time during a war, in his case 1849 and 1859, was counted twice for this matter he had reached the necessary 45 years of service and asked for his retirement which was granted on the 1st of May 1889. For his long years of excellent service Generalmajor Paul Bernnart was honored with the award of the knight's cross of the Order of Leopold on the 2nd of April 1889. With his annual pension of 4.200 fl. he settled down at Krems in Lower Austria. On the 8th of January 1892 Generalmajor Paul Bernnart died in the hospital in Tulln (Lower Austria) a few days before his 64th birthday.