The Tancredi Accord was the culmination of two years of covert negotation between the Outworlds Alliance and the Federated Suns during the run-up to the Star League invasion of the Alliance in 2581. The treaty signatories were President Grigori Avellar of the Outworlds Alliance and First Prince Alexander Davion of the Federated Suns, although the bulk of the negotations were conducted by Lawrence Davion, youngest son of Alexander, and Ambassador Amanda Sigur Consadine of the Alliance.
The negotiations were conducted against a backdrop of political assaults against the Federated Suns within the Star League council by the Capellan Confederation and the Draconis Combine, the ongoing Star League campaign against the Taurian Concordat and the launch of the Star League campaign against the Magistracy of Canopus. The Tancredi Accord was an extension of earlier agreements which had allowed for the supply of weapons and materiel into the Outworlds Alliance from Federated Suns sources via the lightly populated world of Tancredi IV.
In the Tancredi Accord, the Outworlds Alliance pledged to cede twelve lightly populated and unindustrialized but water-rich worlds to the Federated Suns. In exchange for these twelve worlds, Alexander Davion agreed to provide covert military aid to the Alliance and to support a fair solution for the Alliance within the Star League council.
The covert military aid supplied by the Federated Suns included military advisors, who played a key part in a number of battles such as those on Haynesville, but more importantly the provision of the Pitcairn Legion, a three-regiment strong BattleMech brigade consisting of personnel from the Armed Forces of the Federated Suns who resigned their commissions for the duration of the Outworlds Alliance campaign. The exact nature of and support for the Legion varied constantly, but they were a decisive element in Operation UNION HOLD, the Star League invasion of the Alliance.
When peace was declared on the 1st of August 2585 following the signing of the Treaty of Cerberus on the 25th of July, eight of the twelve worlds detailed within the Tancredi Accord had been incorporated into the Treaty of Cerberus, and were duly ceded to the Federated Suns, although the Federated Suns ultimately claimed nine worlds. These nine worlds were: Bastrop, Diboll, Haynesville, Hazelhurst, Inner End, Kennard, Pajarito, Pitkin and Tancredi IV.
- Historical: Reunification War, p. 109, "Davion Diplomacy"
- Historical: Reunification War, p. 119-120, "Haynesville"
- Historical: Reunification War, p. 114, "The Pitcairn Question"
- Historical: Reunification War, p. 106, "Reunification War: Outworlds Alliance Front Deployments (2581)"
- Historical: Reunification War, p. 159, "Inner Sphere - 2596"