First off. Everyone remembers the Battle begins trailer that Bungie released which wa first refferred to as CGI by GameTrailers, to no less than 5 hours later be debunked by Bungie personally saying that was a huge compliment because it was ingame.
The following GIF is from that Trailer.
What surprised me more is that this is actually a battle from a mission called tip of the spear the player actually plays. Yes that is the amount of units you'll see during gameplay. This particular level also includes a huge air battle as well as driving alongside a massive cliff.
Reach looks to be so Epicly huge I actually dont think many of us realise just how much more advanced this engine is than Halo 3. Gamespot further confirm that the backdrops are awesome " Tip of the Spear, the game's fourth mission, which turned the lights back on and painted the screen with the glowing orange hues of distant suns and purple/pink alien foliage" "what really grabbed us about Tip of the Spear was the sense of scale. You'll be driving near a mountain cliffside, and off in the distance, a swarm of Covenant and UNSC airships will be doing battle, somehow looking like flies compared to the gigantic UNSC ship that flies overhead and practically blocks out the sky. Later in the mission, you're tasked with destroying a towering spire powering the electromagnetic shield around a Covenant base. To give you an idea of how big it is, this base is used in a Reach multiplayer map, and according to Bungie, it's the tallest vertical play space it has done in a traditional map."
http://uk.gamespot.com/xbox360/action/haloreach/news.html?sid=6272215&om_act=convert&om_clk=newsfeatures&tag=newsfeatures;title;2&mode=previews
