The perfect XCOM run: How Zemalf beat Impossible Ironman with zero deaths

Strategic moves

"In most cases I took an educated guess or calculated risk moving into certain positions, knowing if I activate a group here, I can deal with it, like having a heavy with a rocket ready to shoot," Zemalf says. "I was always thinking ahead to activate aliens with moves left." At least, almost always—he admits that on a few occasions, like the one above, those calculated risks got him in trouble.

A couple LPs later, Zemalf encounters his first UFO crash. Some risky advances pay off by not revealing additional aliens. If they had, he would almost certainly lose two of his soldiers. But this mission, which he calls the most tense situation of the entire playthrough, shows off the side of XCOM that can be maddeningly difficult: missing high-percentage shots (watch below now) .

The encounter starts out easily enough, with one alien totally exposed and at 1HP. But an 85 percent shot misses the mark. And then a 71 percent shot misses. "Welcome to XCOM," Zemalf says under his breath.

A miss from one of the sectoids at point blank range keeps Zemalf's support soldier alive, but the next turn gets even uglier. He reveals three more aliens by advancing too far and spends several minutes considering every possible option.

"Looking back at it, I could've played a lot better, but that's easy to say now," Zemalf says. He makes a mistake by advancing too far, but this situation highlights Zemalf's strength as an XCOM player: he thinks through each strategic option before moving and only commits to the best course of action when he's sure it's the best. And when things get really dicey, XCOM pays back for its earlier cruelty by helping him land three moderate-percentage shots in a row. He wipes out four sectoids in one fell swoop.

Most of the time, Zemalf's aggressive strategy works well. He methodically activates a group of aliens, then tries to take them all out in one turn. He points to an encounter in his ninth LP as an example (watch below now) .

Since this is several hours later in the run, Zemalf already has a MEC trooper in his squad. He uses the MECs as tanks to take hits that his other soldiers wouldn't be able to survive. As he faces a pair of Thin Men, he methodically thinks through each of his soldiers' abilities, using the MEC's collateral damage ability to destroy one alien's cover, and a grenade to take out the other's cover. That gives him better odds of landing shots with his remaining troops, and he never has to leave cover to fire.

"It's kind of hard to describe my own style, but based on the comments I get, I think I'm playing more aggressively than many others," Zemalf says. "When I have activated alien groups, I play very aggressively to take them out as fast as possible. I think that was key in not losing anyone. The game doesn't get any chance because of the mechanic of how the groups spawn—if you can take the one group out that you activated, before they even get an action, they can't shoot you, and then you more or less can't lose anyone."

Being able to take out alien groups so expediently took some smart base planning early in the game. Zemalf aimed to get as many satellites up as he could in the first three months of the game, which would prevent the XCOM countries from panicking, leaving the project, and denying him crucial resources. He also rushed to build a MEC early and to research laser weapons, which he'd need to deal with the HP buffs aliens get on Impossible difficulty.

Still, it took luck to get him through those first few missions with inexperienced, ill-equipped troops. "Getting hit [early] and not getting a lethal hit is lucky, and I had quite a few of those early on," Zemalf says. The heavy soldiers' rockets and grenades help him get through those early missions. Later he favors snipers and assault troops over heavies, because their explosives could destroy alien weapon fragments he needs for research.