Vienna's population, as the Ottomans advance towards the city, organizes an ad-hoc resistance formed from local farmers, peasants and civilians determined to repel the inevitable attack.

The defenders are supported by a variety of European mercenaries, namely German Landsknecht pikemen and Spanish musketeers sent by Charles V. The Hofmeister of Austria, Wilhelm von Roggendorf, assumes charge of the defensive garrison, with operational command entrusted to a his brother-in-law, a seventy-year-old German mercenary named Nicholas, Count of Salm, who had distinguished himself at the Battle of Pavia in 1525.

Salm arrives in Vienna as head of the mercenary relief force and sets about fortifying the three-hundred-year-old walls surrounding St. Stephen's Cathedral, near which he establishes his headquarters.

To ensure the city can withstand a lengthy siege, he blocks the four city gates and reinforces the walls, which in some places are no more than six feet thick, and erects earthen bastions and an inner earthen rampart, leveling buildings where necessary to clear room for defenses.

The Ottoman army that arrives in late September has been somewhat depleted during the long advance into Austrian territory, leaving Suleiman short of camels and heavy artillery.

Many of his troops arrive at Vienna in a poor state of health after the tribulations of a long march through the thick of the European wet season and of those fit to fight, a third are light cavalry, or Sipahis, ill-suited for siege warfare.

Three richly dressed Austrian prisoners are dispatched as emissaries by the Sultan to negotiate the city's surrender; Salm sends three richly dressed Muslims back without a response.