I really like this episode for several reasons that Halo haters will hate it
I love the humanization of the Spartans and how the team is falling apart, this is part entertainment trope ( the character who has seen things that are covered up so even his closest friends don't believe him but he will be vindicated) but also part realistic given how Master Chief behaved. I love how Riz has been affected by her serious wounds in the last season finale and setting her up for a life outside the Spartan program but we also know that apart from going AWOL she will not be allowed to leave and have that life.
Ackerson is a fascinating character to me - first appears to be the stereotypical secret intelligence "I know more than you do!" asshole but this episode humanized him to a degree and i actually agree with his reasoning and actions. He knows humanity has no chance to hold Reach and it would be futile to expend ressources in a fight they can't win so strategic reasoning is to save vital ressources such as command personnel like Keyes for the coming fights and do the best they can on Reach, that's all they can hope to do and it's a brutal but necessary decision. I'm just a bit annoyed that Keyes, an admiral, failed to see the hard reasoning and is doing the Hollywood/failed hero leader thing and intends to go down with the ship ( he won't i guess but still).
There is so much going on behind the scenes and poor Master Chief has struck a hornets nest with his refusal to be a good and obedient soldier, this is also great and puts it a level beyond the games when they slowly peel back the machinations that are going on.
My big question is now if they will sacrifice Silver Team for maximum emotional impact as they have been developing them since season 1 and making us care for the characters and send Master Chief to Halo on his own, following the original storyline more closer. It would be a really bold move and if they do i would applaud it because too many shows pull their punch at the last second afraid to alienate viewers but i see it more like challenging the viewer and giving them an emotional experience.
I doubt that explosion is the actual start of the Invasion - it's episode 4 of 8 and i can't see them pulling off 4 episodes of even more expensive all out action but when it happens it will be awesome i'm sure.