"No less than ten thousand gladiators fought in the feasts which Trajan gave to the Romans . . . " (Philip Schaff, History of the Christian Church, Volume 2: Ante-Nicene Christianity, Scribner's, New York, 1889, page 95.)
Roman Emperor Trajan had his reasons for celebrating in such a lavish fashion in the games. In 117 A.D., his conquering of the Dacia region (west of the Black Sea) catapulted the empire to reach the largest territory that would ever be under its control. Under Trajan, the empire controlled 2.5 million square miles (6.5 million square kilometers) of territory.
Because of the Emperor's (or a rich citizen's) financial backing, a visitor to the Coliseum could watch animals hunted, or the execution of prisoners or even gladiators fighting. The number of men who died while battling for Roman amusement was incredibly high. Estimates are that, during the time of the early New Testament church, gladiatorial losers had their life ended about 25% per cent of the time. By the third century A.D., this amount was almost 50% (Fik Meijer, The Gladiators: History's Most Deadly Sport, page 61)
In 186 Rome initiated wild animal hunts. A few years later it started the gruesome practice of allowing wild animals to kill condemned people. Such events proved popular. Augustus, during his rule, conducted games where 3,500 wild animals died. The notorious Nero, in a single day, once had hundreds of bears and lions killed. The vast quantity of exotic animals from Africa imported was such that some of them were becoming difficult to find and capture.
The lone voice of protest against the carnage of such Roman events came from Christians. Believers stayed away from the amphitheaters, a practice promoted by church leaders such as Tertullian (160 - 225 A.D.). The shear brutality to both humans and animals was the primary reason Christians opposed the games. The blatant disregard for suffering and life itself promoted by Rome as sport, especially involving gladiators, ran counter to the teaching of Jesus and the early church. Tertullian even denounced the practice of eating meat killed during the violent events. He stated that consuming such meat from animals who took the lives of humans was a version of cannibalism.
One Bible passage cited by both Christians and Jews in condemning the games is in Psalm 1.
"Blessed is the man who walks not in the counsel of the ungodly . . . nor sits in the seat of the scornful . . . " (Psalm 1:1 - 2, NKJV)
Being at the Coliseum during such massive Roman events easily qualified for sitting at "the seat of the scornful!"
As was previously stated, Jewish people were also against the Roman games. The oral law of the Jews stated only two reasons for anyone to attend these festivities. The first is to argue for the sparing of the life of a fallen gladiator. The second is to testify on behalf of a dead gladiator's widow so that remarriage would be possible. A Jew could attend IF they did not succumb to the temptation of watching what happened on the field as entertainment. This task of avoiding the lure of grusome interactions, however, proved difficult.
The end of it
Eventually, pressure from Christians brought about the end of the Roman gladiatorial games, especially at a time when crowds attending such spectacles were dwindling. Philip Schaff quotes a 19th century historian in regards to the role Christians played in ending this violence endorsed by the Empire.
"There is scarcely any other single reform so important . . . the suppression of the gladiatorial shows . . . (the credit for which should be given entirely) to the Christian church."