Their wars had been ranging across the cold and dying planet for ages before we landed there. The lines of the belligerents surged back and forth for uncounted millennia. The younger of the two Alliances gained ground almost the entire time, its empires sometimes sprawling across whole continents. Theirs is a war of immigration, of conquest, and of replacement. At the same time, it is a struggle to obtain a precious, dwindling resource- the primordial element of life itself.

Our primal landing parties were ill-equipped. We did not have the tools or the knowledge to understand what was going on. We were only dimly aware that such a war was even being prosecuted, not for lack of intellect, but because the belligerents are so subtle, so sublime, about their business. The beings of the Alliances live on a different timescale. They wage their wars with weapons invisible.

We had other distractions back then, very different problems from the underlying war between the Alliances. We had to deal with their auxiliaries, their mighty armies of huge, intrusive creatures, fantastical orcs of every description. These we understood all too well. Bright and beautiful creatures, but we were in their way and them in ours. Both Alliances were careful to keep their suzerainties of beasts- their welfare recipients- well fed, at our peril:

We were forced to live as nomads, hiding in the woods, seeking refuge from them in caves, flummoxed, stymied. Any road we tried to build became a line of attack; any field we tried to plant became a feeding ground for the glorious armies. We could not make the numbers and the cities of civilization. Our tribes remained small for untold generations, wandering in the wilderness, battling with the multitudes of giants in those days. All that we could do was just survive.

In those long-ago times, and every once and awhile, one particular type of massive creature would suddenly be disappeared, as if teleported off planet. There was a pattern to it- an enormous raptor gone over here, a gigantic lizard vanished over there, each the largest of their kind. The struggling Alliances could no longer afford their most extravagant luxuries. The giants were getting smaller.

In their scramble to extract atmospheric Carbon from a dwindling supply, the ancient War Between the Plants had taken a new and deadly turn. These occasional losses of their gargantuan dependents were the distant early warnings of the carnage that was to come.

There was an event like this before, long before the grasses, when the air was rich with Carbon and the Alliance of the Trees ruled the world from pole to sunny pole. The pace of life was much quicker then, the plants grew so fast that they could feed creatures far larger than the orcs of our time. The stupendous Carbon levels fell then, too, and the stupendous creatures along with it, never to return.

When the primal grasses landed on the planet they lived there in small numbers, struggling against their tall and mighty opponents, seeking refuge out on the fringes of the wilderness for untold generations. As the Carbon levels continued to drop, the battlefield advantage went to the Alliance of the Grasses. They slowly marched across the continents, battling the giant trees, prevailing, trailing scrublands and deserts in their wake as the Carbon running lower and the world getting colder. After eons of this empire-building, we had arrived in time to witness what promised to be their final battle.

The atmospheric Carbon was down near a level not far above the minimum of what growing plants need, not too far away from The End. A switch was thrown somewhere; the weather mysteriously took a turn for the worse; a tsunami of ice came in from the North. Along with the ice came something even more terrible- the precious Carbon dropped to the lowest it had ever been in the history of the world, right down near the redline. All of the plants of both Alliances, along with all of the animals that depend on them, were in deadly peril, but some were more imperiled than others.

Unbeknownst to us, long before we arrived, a motley assortment of shady characters amongst the Alliance of the Grasses had quietly developed a biomolecular super-weapon of appalling competence. Their astonishing C4 mechanism can vacuum up all of the Carbon out of the air around them, leaving little behind for the neighbors. These shock troops of the grasses had lain in wait for ages, waiting for the right conditions to prevail. Now their weapon came to play.

Fields of C4 grasses vacuumed up the Carbon around them, starving out the other plants and all the types of animals that ate those plants. The trees fell back, unable to stop the onslaught of the Alliance of the Grasses they fell back in a full rout, back to huddle in their warmer, ancient strongholds, there to await their final destruction. Millions of animals were killed; hundreds of different kinds went extinct, gone forever.

Something stopped it. The mysterious switch was thrown the other way. The weather got better. The Carbon level came off the redline. The lights came back on. We looked around in vain for the armies of the orcs: they had vanished from the battlefield. Many of them were exactly the ones that could not eat the C4 grasses. They had left it all to us. In the quiet aftermath of the cataclysm we came forward to plant our fields and build our cities.

The advanced C4 tech is much more than merely an engine of mass destruction. There is a certain air of desperate plan about it. Just because nuclear arsenal doesn’t mean launch. Better to let it hang like the Sword of Damocles. A motivator. C4 is the last card in the deck for life on the cold and dying world, the one to be played as the aerial Carbon finally runs out. Or at least it was until we arrived with our fossil-fueled machines, just in the nick of time as heroes often are.

Now there are giants on that planet again: taller than any tree, larger than any dinosaur, flying higher than any wings. Because of these miracles and the fossil fuels we burn to build, every summer becomes greener, more luxuriant, more difficult to ignore than the summer before. Habitable zones climb the mountains and the latitudes. The deserts become scrublands; the scrublands become grasslands; the trees retake the grasslands once more.

Soon enough, King Coal retakes his throne, the most effective atmospheric Carbon enrichment for now. Robotic fleets of trimmer/chipper/shredders patrol the roads, beating back the fast-moving jungle. We perfect autonomous, self-repairing, and nearly immortal machines to strip mine the limestone and return its Carbon to the quick, holding the levels up to an ideal which is several times what they are today. Perhaps someday we learn to warm the globe and arrest any future Ice Ages as we rise to command the gates of the central star.

If you are one of us in that star system, landed on the planet in question: have a look around. Observe the massive growth rings on the younger trees. Observe the faster-growing plants all around you next summer-

and quickening ever after.