The Old Testament and the Torah, relates mans attempt to be as pure as God, and it was a failure, man couldn't make it. In the New Testament is the new covenant, part of the Godhead, Jesus, came to earth in flesh and paid for our sins so man in the flesh, unable to overcome sin, can lay their sins on Jesus and accept the Holy Spirit that makes sin a hated thing in oneself to be overcome.
God has taken a hands off attitude as far as individual punishment goes allowing each man his lifetime to make his decision. We are told to live in peace with all other men as much as possible until He returns. The Jews, still the apple of God's eye have preserved for all these many thousand years His word, were expecting a Messiah, not the Messiah, to come defeat their enemies through war. Jesus came in peace and delivered all men from their worst enemy death.
The Jews as Jesus said, "missed the hour of their visitation". So you are right earthly battles is not what Jesus was here for. As far as who Muhammad is, we have no idea, it seems his teachings lead to destruction and death, totally against the principles and commands of Jesus.