I am having a question regarding forks. We had a discussion about attacks on bitcoin in class recently. One of the attacks was about how an attacker gains some advantage if he is able to mine a block and hold it back. He would release the block only if another miner finds a block in order to create a fork.
After that we had been discussing if it would be possible to create a fork somewhere in the past. Let's say an attacker decides now I would like to fork the blockchain 2 days ago. He starts to mine blocks from the time in the past and tries to create a longer chain. As soon he has a longer chain, he releases it and hope that the chain forks.
My question is now: Is that actually possible? Is it possible to fork the blockchain somewhere in the past if we are able to create a longer chain and release it later?
I tried to find some information but all I get is hard fork information. Thanks in advance