First what was Justinian’s, or rather his general's, (Belisius) victory in 538? Was it "extinguishing" the Ostrogoths? No, it was the retaking of ROME (the imperial city) from the RULE of the Ostrogoths, and out from under Ostrogoth' reign, and thus placing it under ROMAN LAW-- that law which Justinian had codified just a few years earlier-- which contained the declaration that the Pope (not necessarily a specific individual pope, as there was a removal of Pope Silverius and the replacing of Pope Vigilius right then in 538) but the recognized pope, who was seated in Rome, was BY THE NEWLY CODIFIED ROMAN LAW, head of all churches and in charge of "dealing" with the "heretics".

It is true that the Goths were not defeated as a whole nation until several years later, it is true that after this victory of Belisarius in 538, the city of Rome itself was twice retaken by Totila, the new leader of the Goths. But he never ended up setting up any Empire there.
First, in 545, Totila laid siege to Rome, which held out for about a year. Belisarius, who was sent by Justinian to defend Rome, was given hardly no troops, and could not withstand the siege. Rome fell in December 546. Totila considered destroying the city, but Belisarius wrote him in protest, pointing out how it would damage his reputation if he destroyed a city of such beauty, and Totila gave up his plan and instead evacuated Rome, taking with him the senators and sending the rest of the populace into Campania.

As soon as Totila left Rome to recover other cities, Belisarius re-entered Rome, rebuilt and repopulated it and prepared it to withstand yet another siege. Totila returned with his troops and attacked, but was repulsed and had to withdraw. Belisarius was not receiving much support from back home-- Justinian was busy fighting the "new Persians". Belisarius, discouraged, went home.

In 549 Totila again attacked Rome and entered the city, but then he decided to "punish" the Sicilians and crossed to Sicily, to slaughter the inhabitants. Justinian was shocked and sent troops to get rid of Totila. Narses (Justinian's General) defeated Totila's armies and Totila was killed. This was 552-- a little over two years after he entered Rome.

It was Totila's “recapturing of Rome” which was very short lived!

According to “A Survey of European History” by Ferguson and Bruun, page 157:

THE ROMAN CODE OF LAW was IN FORCE-- IN ROME--
And that law gave the POPE the LEGAL position as head of all churches with authority to deal with all heretics.

Yes, there were lots of wars-- but the Roman code of law, THAT LAW WHICH LEGALLY DECLARED THE POPE HEAD OF ALL CHURCHES, and defender against all heretics, was established in ROME in 538, and even though suffering some political setbacks during that time, that Roman LAW was ALWAYS brought into force again and stood as THE LAW, in Rome, from 538 until Napoleon’s new CODE OF LAW replaced it 1260 years later.

Totelia’s victories were short, very short lived, Rome was RECOVERED for Justinian by Narses.

No, dominion, no new power was SET UP in Rome other then the power of the Papacy.

There was NO CHANGE in the law which decreed that now the Pope was "head of all churches" and responsible to "deal" with all "heretics".

Thus in 538, the "saints" were literally "given into his hands, at the beginning of the 1260 years, in 538.

(Main Resource: "Justinian the Great" by Tomas Fitzgerald As well as other encyclopaedias and history books.)

For more on the significence of 538 see my webpage:
The 1260 Day/Years

The second problem with the traditional interpretation is its failure to account for the basic meaning of this prophetic period, namely, a time in which God's people are persecuted on the one hand and are protected on the other hand. It is evident that the persecution and protection of the church did not begin in 538 nor did it end in 1798.

The 1260 years are consistently linked to the time period after Christ's death and resurrection when an earthly power will have primacy over God's saints and seeks to destroy them.