“The Apostles received the gospel for us from the Lord Jesus Christ who was sent forth from God. So then Christ is from God and the apostles are from Christ … having therefore received a charge, and having fully assured through the resurrection of our Lord Jesus Christ” (Clement of Rome, around 95 A.D. from 1 Clement paragraph 42)
Jesus taught the apostles and the apostles passed the reality of the ressurection onto early Christians like Clement of Rome.
Ignatius
Ignatius was thrown to the lions in the Colosseum at Rome for the amusement of the crowd. This occurred around 117 A.D.
"Trajan pronounced sentence as follows: We command that Ignatius, who affirms that he carries about within him Him that was crucified, be bound by soldiers, and carried to the great [city] Rome, there to be devoured by the beasts, for the gratification of the people."
"When the holy martyr heard this sentence, he cried out with joy, I thank you, O Lord, that You have vouchsafed to honour me with a perfect love towards You, and hast made me to be bound with iron chains, like Your Apostle Paul. Having spoken thus, he then, with delight, clasped the chains about him; and when he had first prayed for the Church, and commended it with tears to the Lord, he was hurried away by the savage cruelty of the soldiers, like a distinguished ram the leader of a goodly flock, that he might be carried to Rome, there to furnish food to the bloodthirsty beasts."Read more about the death of Ignatius
Polycarp
Polycarp was burnt to death at around 155 A.D. when he refused to revile Christ.
"... the magistrate pressed Polycarp hard by saying 'Swear the oath, and I will release thee; revile the Christ,' Polycarp said, "Eighty and six years have I served Him, and He never did me any injury: how then can I blaspheme my King and my Saviour?"
After Polycarp was pressed more by his accusers he responded; 'You threaten me with fire which burns for an hour, and after a little is extinguished, but are ignorant of the fire of the coming judgment and of eternal punishment, reserved for the ungodly. But why do you tarry? Bring forth what you will.'
Read more about the death of Polycarp
Nothing has changed. In the 21st century, we too can have the same confidence the apostles had that Jesus did indeed rise from the dead.
“We did not follow cleverly invented stories when we told you about the power and coming of our Lord Jesus Christ, but we were eyewitnesses of his majesty” (Peter the Apostle - 2 Peter 1:16).
“That which was from the beginning, which we have heard, which we have seen with our eyes, which we have looked at and our hands have touched—this we proclaim concerning the Word of life” (John the Apostle - 1 John 1.1).
Reference “He Walked Among Us”, Josh McDowell, Here’s Life Publisher, San Bernardino, Third Printing 1989. This book is full of excellent information with regards to the historical accuracy of the bible.