Anxious for employment, and remembering, perhaps, the manner in which Frederick II. had insulted him at his levée in Berlin, the enterprising spirit of Loudon induced him to visit Vienna and solicit a command against Prussia; but having left his regiment without obtaining leave of absence, he was on the point of being reprimanded and ordered back to Croatia, when by good fortune he obtained the friendship and patronage of Prince Kaunitz, the head of a noble family, whose possessions lie on the Iglau in Moravia. By the prince's interest he was appointed Lieutenant-Colonel of eight hundred Croats. These wild and hardy troops were destined to be ordered on every desperate service, and as their mode of fighting resembled in every respect that of the Pandours, Loudon was well fitted to command them; more especially as he had acquired their dialect while quartered in their native province. They were all clad in short waistcoats with sleeves, long white breeches, light boots, and rough huzzar caps. They had each a long firelock with a rifle barrel and short bayonet, a crooked sabre, and brace of pistols. This corps formed part of five thousand Croats levied by the Empress-Queen for the new war against Prussia. Like the Pandours of Baron Trenck, they had no pay or provisions, but such as their swords and the terror of their presence won them; and as irregular troops they were a scourge wherever they marched.
On the 29th of August, 1756, the King of Prussia entered Saxony at the head of seventy battalions of foot and eighty squadrons of horse, in three columns, which marched by three different routes, but formed a junction at Dresden and captured it. The Elector, who was King of Poland by the title of Augustus III., took refuge in a camp at Pirna, while Frederick marched into Bohemia and found the Austrians encamped at Lowositz under Marshal Count Brown, who was defeated there in October; and after a long and bloody contest forced to retire in rear of Egra.
It was at this time that Loudon with his Croats joined the Austrian army; and in the disastrous retreat which ensued after Lowositz, he narrowly escaped when a hundred of his grenadiers were slain by the Prussian hussars. During Marshal Brown's retreat out of Saxony, Loudon took by surprise the town of Estchen at the head of five hundred men, and destroyed two squadrons of Prussian hussars. This was his first exploit, and it was deemed the most brilliant of the Austrian campaign.