[1] Segni was a small town, a former Roman colony, sited approximately halfway between Rome and Montecassino.

[2] By the beginning of the 20th century, it had become apparent to the papacy that the suburbicarian bishops had become overburdened with the responsibilities of their curial and diocesan duties.

The diocese of Sabina and Velletri are stated to already have had a suffragan bishop, whose powers were in any case henceforth augmented and regulated by Apostolicae Romanorum Pontificium.

In a decree of the Second Vatican Council, it was recommended that dioceses be reorganized to take into account modern developments.

[9] A project begun on orders from Pope John XXIII, and continued under his successors, was intended to reduce the number of dioceses in Italy and to rationalize their borders in terms of modern population changes and shortages of clergy.

There was to be only one episcopal curia, one seminary, one ecclesiastical tribunal; and all the clergy were to be incardinated in the diocese of Velletri-Segni.