He then participated in the 1710–11 Pruth River Campaign, was appointed to the honorary post of kapıcıbaşı, and then sent to the Rumeli Eyalet where he served as commander of the Christian irregular militia, the armatoloi.

In this role he served in the 1715 campaign that recovered the Morea from the Venetians, where he so distinguished himself that he was promoted to the rank of pasha with two horse-tails, and appointed governor of the Sanjak of Tirhala.

He also encouraged the efforts of the French army officer Claude Alexandre de Bonneval in reforming the humbaracı artillery corps after Western models.

[5] After his dismissal, Topal Osman served briefly as governor of the Trebizond Eyalet and of Tiflis, before being recalled and, as the Empire's most experienced soldier, appointed serasker of Anatolia in the Ottoman–Persian War of 1730–35.

Aided by Topal Osman's clever stratagems, the Ottomans inflicted some 30,000 casualties on Nader Shah's army and forced it to withdraw, although they lost 20,000 in turn.

Topal Osman's army at Kirkuk had been weakened by the Ottoman government, with experienced men transferred west and replaced by low-quality levies, although he retained a numerical superiority over the Persians.

A Persian soldier cut off Topal Osman's head and brought it to Nader Shah, who, after ordering his opponent's corpse found, returned his remains to the Ottomans, out of deep respect for an adversary he considered to be worthy.