3 Truly wonderful is the work he was able to effect during his reign of little more than thirteen years. He was the restorer of Christian life in its entirety, stimulating the devotion of the faithful, the observance of the monks, the discipline of the clergy, the pastoral solicitude of the bishops. Most prudent father of the family of Christ that he was (Joann. Diac., Vita Greg. ii. 51), he preserved and increased the patrimony of the Church, and liberally succored the impoverished people, Christian society, and individual churches, according to the necessities of each. Becoming truly God's Consul (Epitaph), he pushed his fruitful activity far beyond the walls of Rome, and entirely for the advantage of civilized society. He opposed energetically the unjust claims of the Byzantine Emperors; he checked the audacity and curbed the shameless avarice of the exarchs and the imperial administrators, and stood up in public as the defender of social justice. He tamed the ferocity of the Lombards, and did not hesitate to meet Agulfus at the gates of Rome in order to prevail upon him to raise the siege of the city, just as the Pontiff Leo the Great did in the case of Attila; nor did he desist in his prayers, in his gentle persuasion, in his skillful negotiation, until he saw that dreaded people settle down and adopt a more regular government; until he knew that they were won to the Catholic faith, mainly through the influence of the pious Queen Theodolinda, his daughter in Christ. Hence Gregory may justly be called the savior and liberator of Italy - his own land , as he tenderly calls her.
Source: Iucunda Sane (Vatican.va)