Winter is upon us. And though you may find yourself whiling away these cold months with nothing more than hot cocoa and stories around the fire, it may be that you are called to battle. Perhaps you will be drafted into a snowball fight, in which case, you had better be prepared. Maybe, like so many cold warriors before you, you'll find yourself in want of fortification. Maybe you and your hapless team will cower behind trees or dig trenches in the snow. The most ambitious among you will take it upon yourselves to make a snow fort.

Will it have walls? Maybe there will be a igloo portion with tunnels for safety? Will there be battlements and ramparts? Are you sketching out plans right now, as you read this? Would you like to make the best snow fort?

If so, we'd like to humbly suggest that you consider pykrete for all your snow fort construction needs. Pykrete is a composite material made of a mixture of wood pulp and ice. Named for its inventor Geoffrey Pyke, pykrete was an experimental material developed during the mad science heyday of World War II.

At a time when steel was starting to run into short supply, Pyke looked at ice, a material that can be formed for a fraction of the energy cost of steel, as a potential building tool. Early experiments ran into problems — ice is prone to being brittle — but they came across research that showed that if you mixed in cellulose with pure water, that the resulting stuff, when frozen, turned out to be quite durable.

How durable? Let's put it this way: Would you like a snow fort that is bullet-proof?

Pykrete's stopping power is similar to that of brickwork, except that when it comes to building with it, you can mold it like concrete and then you can carve it like wood. This makes is really versatile for construction, opening up all kinds of possibilities for the grand hall of your awesome ice castle. Amazingly, because of the reduced heat transference between the two component materials, it even melts more slowly than regular ice.

So what happened to this wonder material? The project that led to its invention, called Project Habakkuk, lost favor. Its goal to create an unsinkable aircraft carrier for the northern theater became less important as airplanes developed longer and longer flight ranges. Which is too bad, because a self-repairing ice island armed with freeze-rays still seems like a pretty amazing idea.

Instead, pykrete has fallen by the wayside as an offramp to materials history. Every now and then visionary architects, futurists, myth-busters, and libertarian dreamers resurrect the material, but so far no one has taken it seriously enough to test it at the large scale required to find out if it's worth using. Except for you, and your amazing snow fort.