Ended the War of the Keys between Frederick II and Pope Gregory IX, restoring papal-imperial relations and lifting Frederick's excommunication.
Key Facts
- Date signed
- 23 July 1230
- Location
- San Germano (present-day Cassino)
- Conflict ended
- War of the Keys (begun 1228)
- Excommunication lifted
- 28 August 1230 at Ceprano
- Key papal negotiator
- Cardinal Thomas of Capua
- Frederick's main concession
- Surrender of special rights over church in Sicily
By the Numbers
Location
Cause → Event → Consequence
The War of the Keys had been ongoing since 1228, pitting Holy Roman Emperor Frederick II against Pope Gregory IX. Frederick's excommunication and the conflict over Sicilian church rights created a deep rupture between empire and papacy. Negotiations began in November 1229 at Frederick's initiative, though the Lombard League, allied with Gregory, initially obstructed progress.
On 23 July 1230, Frederick II and Pope Gregory IX concluded the Treaty of San Germano, largely restoring the territorial status quo ante bellum. Frederick recognized the Papal State, Gregory acknowledged Frederick as legitimate king of Sicily and emperor, and a general amnesty was issued. The main concession from Frederick was relinquishing his special rights over the Sicilian church.
On 28 August 1230 at Ceprano, the peace was sealed with Frederick's formal readmission into the church, ending his excommunication. The treaty was widely regarded as a victory for the emperor, as he retained his imperial and royal titles with minimal territorial losses, while the papacy recovered its Sicilian church privileges only in part.
Political Outcome
Restoration of status quo ante bellum; Frederick II readmitted to the church; general amnesty issued; Frederick surrendered special church rights in Sicily
Frederick II excommunicated; War of the Keys ongoing; papal-imperial relations severed
Frederick II rehabilitated into the church; mutual recognition of titles and territories; imperial position largely intact