Von Koller spent his military career ascending the ranks through service in various regiments of the Imperial and Royal Hussars. In 1848, as a batman, he fought on the Austro-Hungarian side in the First Italian War of Independence, at the Battle of Sommacompagna, a skirmish by the Salizone, and the Battle of Custoza. In 1849, he distinguished himself in skirmishes at Borgo San Siro and Gambolò. In 1859, during the Second Italian War of Independence, von Koller was awarded the Knight's Cross of the Order of Leopold for his service. In 1866, during the Third war, he was admitted to the Order of the Iron Crown, Second Class, was promoted to the rank of lieutenant field marshal, and received command of the Imperial and Royal 5th (Nicholas I, Emperor of Russia's) Dragoons. In 1868 he became leader of the lieutenancy in Prague. For this service he was promoted to the First Class of the Order of the Iron Crown and was admitted to the Privy Council.