When 2K Marin first announced that it was taking on the much-loved XCOM strategy franchise with a first-person shooter reboot, you could hear the collective wailing of hardcore XCOM fans from space. What those fans might fail to realise however, is that this is no ordinary reboot and the series' strategy roots look to be laced throughout the game's DNA like a stick of rock. This is a reboot in the same vein as the new Battlestar Galactica or Batman Begins, with a brand new universe says Director of Development Morgan Gray, who is on hand to take us through XCOM's “peanut butter and chocolate” combo of classic strategy and shooter action at E3 2011.

It's 1962 and the US of A finds itself gripped by an unknown alien threat, which gives rise to the XCOM organisation, formed exclusively to fight against said alien threat and gather research on the extra-terrestrial enemy. You play as Agent Carter, leading a team of field agents on a variety of non-linear missions that you can select in any order you see fit. Our demo presentation begins with Carter stood in his office - which will act as your game hub – while just outside the door is a window into the XCOM control centre, where your team is working on research and other exciting advancements with alien technology that you'll be able to wield in the game.

In the control centre you'll meet Leon Barnes in a more refined Fallout-style dialogue exchange. Barnes is in charge of managing your pool of agents and will aid you in selecting your crack team to take with you into missions. There are several different operatives to choose from with different specialities, but for this particular objective, Carter picks Master at Arms Roland Vancomerback and Commando Kevin Escher, both of which have been levelled up to level 2 and have been given a series of upgrades. It's worth noting that you can upgrade and customise your agents in any way you like, adapting them to the task at hand and giving you a variety of choice for your three-man team.

With our team duly assembled, we meet with our co-ordinating officer Angela who presents us with a series of missions marked as red triangles on a tactical map of the US. You can tackle the missions in any order, but some will be of more value than others, such as the mission to locate and extract Dr. Weir in Rosemont, Georgia. Successfully rescuing Weir will unlock new research that will be of use in subsequent missions, providing a valuable boost to weapons and tech. With this in mind, Carter takes the Sky Ranger craft to the insertion point and hits the suburban streets with Escher and Vancomerback in tow. Our first port of call? A military checkpoint, where hopefully we'll find some additional aid.

Obviously, there's no such luck as the military encampment is a deserted smouldering hole. Moving through a nearby diner, it seems far too quiet and further exploration around the military zone reveals burnt out cars and smoking bullet holes, all of which aren't particularly encouraging. Inside, we come across a soldier who at first glance appears to be a lone survivor, when in fact he's a malevolent bodysnatching Infiltrator, one of the multiple types of alien Outsiders. Infiltrators can assume human forms, but this one quickly reveals his true nature, suddenly leaping aggressively at Carter and his men. Outside, the fight continues with a small unit of Outsiders throwing up an energy shield around one of their devastating turrets.

In a nod to XCOM's original 'Battlescape' mode, the tactical view enables you to slow down time and issue commands to your squad, with each action costing you a certain number of time units, of which you're given a finite amount to use. In this situation, we need to outflank the Outsiders and disable their shield and turret, which is where the tactical view comes into its own. Using a disruptor at a cost of three of our ten time units, we manage to attract the Outsiders' attention, giving our boys the perfect opportunity to bring down the shield at our behest. While the Outsiders smartly single Carter out as the main threat, the squad draws their attention, enabling us to dash around to destroy the turret's control panel and take out the aliens with a deft flanking manoeuvre. Taking down the turret this way preserves it, meaning that Carter is able to capture it to be deployed at an appropriate juncture for a one-time use, or take it back to the lab for a weapons research boost.

It's this kind of micro-strategy that will keep you on your toes throughout XCOM, Gray assures us, as he also notes that he could have just as easily destroyed the turret, but would have lost the benefits as a result. There be plenty of tactical decisions and choices like these to make on XCOM's battlefield, clearly demonstrating that it's so much more than a straightforward run-and-gun shooter. Moving on and Carter and co. can see that they're getting closer to more pockets of Outsider invaders, as the environment is increasingly being terraformed with the aliens' distinctive blue crystalline structures engulfing cars, roads, gardens and houses. Hot on the trail of Weir, Carter, Escher and Vancomerback enter an office building, where through an internal pane of glass, a strange floating insectoid-like Outsider snakes its way through the air, taunting a poor soul that it then rapidly jams through the wall, leaving his torso poking through into the corridor on our side.

There's no reasoning with the Outsiders, and as they apparently detect our vicinity to Dr. Weir, the aliens send a Titan into the square outside, which spits fiery death in whatever direction it faces, carving through buildings like a knife through butter and causing massive destruction in its wake. Using the captured turret, Carter expends its potential for research – although he can always find another turret to take back home later on – but gets a massive advantage as it homes in on the enemy. With some smart tactics and the use of a powerful weapon fabricated using alien tech earlier, the huge Titan laser is captured and safely stowed for research or later use.

Outsider reinforcements descend upon the square, so the Titan is deployed to make short work of them while we watch the carnage unfold. Somehow, Vancomerback is incapacitated amid the chaos, so Carter throws an energy shield over him and moves in for a revival. Carter and his crew then get back to the business of tracking down Weir only to find him being pulled into a huge glowing vortex. With seemingly no thought for self-preservation, Carter runs in after him and finds himself landing face down on top of a pile of debris. The debris falls away and reveals a vast, gaping maw filled with monolithic stacks of alien cubes, moving and locking into shape. It's an ominous, terrifying sight, hinting at something far beyond a simple invasion is at work. The Outsiders will stop nothing short of complete domination judging by this breathtaking conclusion to the demo, and it'll be up to you to prevent that from happening.

XCOM is looking remarkable and was a genuine surprise at this year's E3. The game looks to have come on leaps and bounds since its showing at E3 last year and 2K Marin seems to have gone to great lengths to preserve the strategical heart of XCOM, despite the fact that it's all draped in FPS clothing. The promise of both story-driven and non-narrative themed missions, as well as the tactical view and the depth of strategical choices should hopefully please the die-hard fans while enticing newcomers, making XCOM quite clearly one to watch for 2012.

XCOM is due to invade on March 6th, 2012 in North America and March 9th, 2012 in Europe.