Siege of Tortona

Siege of Tortona
	Part of Guelphs and Ghibellines
Date	13 February – 18 April 1155; (2 months and 5 days)
Location	Tortona44°53′39.001″N 8°51′56.002″E / 44.89416694°N 8.86555611°E
Result	Imperial victory
Belligerents
Holy Roman Empire; Commune of Pavia; Margraviate of Montferrat	Commune of Tortona; Commune of Milan
Commanders and leaders
Frederick I, Holy Roman Emperor	Obizzo Malaspina
Strength
5,400–7,200+ 5,400–7,200 1,800 knights Pavian militia; Montferrat's forces	300+ 100 knights; 200 archers; Tortonian militia; Malaspina's men
Casualties and losses
Unknown	Garrison captured; City burned
	class=notpageimage\| Location within Italy Siege of Tortona (Mediterranean)

The siege of Tortona in 1155 was the first major military engagement resulting from Holy Roman Emperor Frederick Barbarossa's ambition to enforce Imperial hegemony in Italy.