Where was Optimus Prime all that time at the end of Transformers?

Late into the final battle of Transformers, the 2007 film, Optimus Prime finally joins the battles, rolling up to the scene in his truck mode with heroic music playing.

Where was he all that time??? Jazz was killed, Bumblebee was severed, and Ratchet and Ironhide were taking heavy blows. Then Prime shows up so late. Was he busy doing something else in a deleted scene I didn’t see? What’s up?

thanks
No he wasn’t fighting Megatron.
When the team gets Bumblebee out from captivity, they go on the highway downtown and meet up with Optimus and the others and they all head down.
On the highway, Optimus kicks the crap out of Devastator, killing him.

They enter the city and see Blackout flying up in the sky low to the buildings, but I don’t see Optimus Prime anywhere.
The next time we see Optimus is when he enters the battle late to fight Megatron who has killed Jazz by that point.
Optimus says “Megatron”; Megatron says “Prime”, then transforms and flies towards Optimus, who jumps to grab him.

Where was he between killing Devastator and fighting Megatron????
(poor Jazz, could have been saved )
Bug, to answer you - I’m talking about the period between Optimus Prime killing Devastator, up until right before he arrives in the clip you showed me on youtube here.

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