The battle code requires you to engage him in combat. Alone.
7 seconds sound clip from The Transformers (1984) - Divide and Conquer TV Series.
You can hear this line at 00:20:25 in the DVD version of the movie.
Quote context
[...]
- We are victorious! Is there anyone in the universe who will challenge the might of Megatron?
- There is one, Megatron! I, Optimus Prime, challenge you!
- He accepted your challenge, leader.
- The battle code requires you to engage him in combat. Alone.
- Then it's just the two of us, Megatron!
- I used too much power against the Autobots! I need assistance!
- How unfortunate. If you cannot fight your opponent yourself, you are not fit to be our leader.
- I am the only suitable leader, anyway.
- Megatron. Do you yield? Yield. For now! Only for now!
[...]