After Jesus turned himself in to the authorities (for a specified purpose), Jesus told the disciples that He is Jesus of Nazareth. But even when Jesus is about to get arrested, Jesus had the disciples in mind.
First, Jesus told the disciples to "let [them] go their way" (18:8). He said this to fulfill His own word where Jesus lost none (18:9). Jesus said these words during his prayer in John 17:12, and Jesus not only had the sense of eternal security but also physical security. Jesus made sure that until the ascension, all of the 11 disciples are alive. In fact, even though they crashed and burned in fear (and with one of them disowning Jesus), all of them eventually found life in Jesus. Whenever Jesus makes promises, he takes them very seriously.
Around the same time, however, Simon Peter, who had a sword, sliced the ear of Malchus, a servant of the high priest (18:10)! Peter slashed because he wanted to protect Jesus. But in response to Peter's sword slice, Jesus commanded Peter to put the sword "into the sheath" since Jesus would "drink the cup which [His] Father has given [Jesus]" (18:11). In other words, Jesus intended to turn himself to the authorities because it is part of the Father's plan to die on a cross on behalf of humanity. Peter at that time did not understand.