At 33 Ambrose had it all - a successful career as a lawyer, an important position as governor of Milan, the approval and friendship of the emperor, and a large estate. Then the bishop of Milan died. At this time, about 374, heresies threatened to destroy the Church. The bishop had supported the Arian heresy that argued against the divinity of Christ. Who would take his place - an Arian or a Catholic? Both sides met in the cathedral and a riot broke out. Public order was Ambrose's responsibility as governor so he hurried to the church and made a passionate speech not in favor of either side, but in favor of peace. He begged the people to make their choice without fighting, using restraint and moderation. Suddenly, while he was speaking, a voice called out, "Ambrose for bishop!" Soon everyone was shouting, "Ambrose for bishop!"
The other bishops of the province were only too glad to have this controversial decision taken out of their hands. But Ambrose was not about to give up a successful career for the dangerous position of bishop - a life- threatening occupation in these heretical times. So Ambrose ran away. When he appealed to the emperor to overturn the decision on the basis that he hadn't even been baptized yet, the emperor answered that he was happy that he chose governors fit for the episcopal office. Ambrose hid in a senator's house but the senator surrendered Ambrose when he heard about the emperor's decision. With nowhere else to run, Ambrose gave in. Since he'd been forced to take the position, no one would have been surprised if he'd decided to keep on living the way that he had before ordination. Instead, Ambrose immediately gave his property to the poor and put himself under the instruction of Saint Simplician to learn Scripture and theology. The Arians thought Ambrose would be "their" bishop because Ambrose had been a member of court and many in government were Arians. But Ambrose used his skills as a lawyer and orator to fight the Arians in church, court, senate, and even the emperor's own family. The same stubbornness that had made him refuse the position in the first place was now his weapon in fighting heresy and pursuing sanctity.
When the Goths invaded the empire and took captives, Ambrose paid out all the money he had in ransom. He said the best and most effective charity was ransoming captives and hostages. He even took all gold vessels belonging to the Church and had them melted down. He said, "It is a better thing to save souls for the Lord than to save treasures. He who sent forth his apostles without gold had not need of gold to form his Church. The Church possesses gold, not to hoard, but to scatter abroad and come to the aid of the unfortunate. "Would not the Lord say to us: 'Why have you let so many needy perish of hunger? Since you had gold, you should provide for their needs'...Could we say: 'I feared to leave the temple of God without ornament.' But that which can't be bought with gold does not take its value from gold. The best way to use the gold of the Redeemer is for the redemption of those in peril."
Ambrose always was more concerned for the poor than for power. He often reproached the wealthy for ignoring the poor: "God created the universe in such a manner that all in common might derive their food from it, and that the earth should also be a property common to all. Why do you reject one who has the same rights over nature as you? It is not from your own goods that you give to the beggar; it is a portion of his own that you are restoring to him. The earth belongs to all. So you are paying back a debt and think you are making a gift to which you are not bound."
When the emperor died, the Empress Justina, an Arian, became regent for her four year old son. Maximus, a former Roman soldier, realized the emperor's death might weaken the empire enough for his army to conquer it. Justina begged Ambrose to negotiate with him. In spite of the fact that she was his enemy, Ambrose went on a diplomatic mission that convinced Maximus not to invade. Justina's idea of showing gratitude to Ambrose was to demand that Ambrose's basilica be handed over to the Arians. Ambrose answered that he would never give up the temple of God. The people were on Ambrose's side. It is possible he could have even started a coup to overthrow Justina. But Ambrose was careful never to say or do anything to start violence. When Catholics seized an Arian priest and were going to put him to death, Ambrose intervened in the name of peace and prayed God suffer no blood to be shed. He sent out priests and deacons to rescue his Arian enemy. Ambrose said, "When I was told the church was surrounded with soldiers I said I cannot give it up but I must not fight." The soldiers came in to the basilica - but they came in to pray.