As the helicopters swooped in, enemy ground-to-air defences opened up and rockets leapt into the sky, leaving smoke contrails in their wake.
We were dealing with a four-man SAS infiltration squad in the previous operation, but in this mission we got to witness the larger US Force Recon squads and heftier firepower they pack, and we watched as soldiers in Force Recon swiftly rappelled down ropes.
As comrades-in-arms began rolling out barbed wire defences, Collier quickly became embroiled in a deadly exchange of bullets in street-to-street fighting. Deft use of flashbangs was made, the grenades lobbed into rooms to stun enemies before going in - but the catch of the odd bullet was inevitable and, similar to CoD 2 and 3, the screen began to turn red when Collier was hit; and heart beats are heard if things get real bad.
Like previous COD games, comrades urge you to objectives, with the game presenting you with a number of paths through levels - although Modern Warfare is by no means 'sandbox'.
Collier stuck with Force Recon and Middle-East operations for two further missions, the first involving the rescue an M1A1 tank - which the soldiers ended up working alongside - and furious street fighting.
It was here that we really got to witness Infinity Ward's attention to detail and the ramped up assault on the senses achieved in the sequel, with walls being crumbled by explosions and sending out puff of dust particles, vehicles being shot apart by bullets and proof of accurately modelled ballistics as the likes of the M249 SAW ripped through walls.
Reeling from the visual and aural bombardment, all we can say about the second mission, a night-time operation to locate and secure a crashed helicopter - very Black Hawk Down - is: nice nightvision.
You can't have a Call of Duty game without multiplayer of course, and CoD 4 supports 32 players on PC and on PS3 and Xbox 360 it'll be between 12 and 16, Collier told us, adding that the developer explored cross-platform between PC and Xbox 360 but decided it wasn't something suited to CoD multiplayer.
Persistent statistics tracking is included to track the likes of kills, matches played and shots to the head and Infinity Ward's packing in an experience system which is linked in with unlockables. Collier explained that the developer hopes the experience system will encourage novices to dip a toe into the CoD 4 multiplayer waters, with weapons being unlocked as experience is bumped up.
CoD multiplayer veterans, though, will be able to progress through the unlocks quickly, and at the high end of the experience system unlock new titles and skins for weapons and character models. Experience levels can be added too, so expect this part of multiplayer to be boosted with download content after the game's released.
We'll have more multiplayer details on the site soon, featuring in an interview with Grant Collier.
So far, so good for Call of Duty: Modern Warfare, although we'd shove the lot of what we've seen to date under the 'frantic-intense' umbrella and have yet to witness any real variation in pace.
However, in those intense bits, the game's lost none of the intensity the series is known for in its transition to a new setting (in fact, if anything - and excuse us for the use of a classic old joke here - Infinity Ward has turned intensity up to 11 for the sequel). It's the little things, the attention to detail, that blend together with the gunplay and make the whole thing explode in your face.
The interweaving plot structure remains an unknown at this stage, but we reckon the developer's made the right decision in ditching the old campaign structure (and WWII - Ed) to introduce a new storytelling mechanism. Let's just hope by the end of it, we've remembered who the main characters are.