When exactly does combat start and surprise take effect?


So say I’m going to ambush an orc. I successfully sneak up on him and I attack. The DM determines that the orc is surprised. The orc happens to get an initiative roll of 19, while I get a 10. How would this work? I can only think of two reasonable resolutions to this.

  1. The orc, having a higher initiative, goes first. Since he’s surprised, he does nothing. Then it’s my turn. If the orc survives my attack, it is now his turn, and being that the orc has already gone through his round of surprise, he can now attack me or whatever, and combat proceeds as normal.
  2. I, having started the combat, go first. If the orc survives my attack, but he is surprised, so he does nothing. It is now my turn again, I attack again. If the orc survives my second attack, it is now his turn, and being that the orc has already gone through his round of surprise, he can now attack me or whatever, and combat proceeds as normal.

Which one of these is correct? neither? Does starting combat secure me a turn/action at the start of initiative order like in option 2? If option 1 is correct, could I ready an action to shoot the orc, effectively granting me a similar first attack as in option 2?

Sorry if this makes no sense.