China had also already started construction for dams on all of the rivers that flowed down to India. When those were nearing the end of construction, they began moving their armies over to the border with India while at the same time sending reinforcements mainly composed of troops from their puppet states over to Russia.
Although everyone knew that a third world war would probably be fought with nuclear weapons, there had been a consensus that doing so would basically be the end of humanity, as not only would a nuke cause a ton of damage by itself, but it would also further deteriorate the ozone layer, therefore making global warming increase at an even more rapid rate.
As for why that mattered, apart from an increase in natural disasters in the future, and the fact that weather patterns would shift was the fact that it would basically eliminate most of the drinkable water found on earth, because due to global warming, not only had the polar caps severely melted, but rivers had begun to run dry.
That plus the fact that those that didn't dry up were filled with trash and plastic particles, and you had a recipe for the total elimination of the human race, that's why cutting off a country's water supply was so effective, as time passed water was constantly becoming more valuable, therefore causing for country's to not be willing to share their own.
It's also why china damming up the rivers connected to India was such a savage move. China was trying to defeat their enemy by letting them die of dehydration if they refuse to become a puppet state.
Going back to how the war was fought, basically, anything other than biological and chemical warfare was a go, except for anything as strong or stronger than a nuclear bomb.
The US populous was mad but not surprised that both communist powers had begun to go on the move simultaneously as it was evident that they would have to do so to stand a chance, so now, the US was forced to make a critical decision.
The US fleet located in the pacific could either be sent to secure Chinese trade routes or to take complete control of Siberia. And although Congress hadn't yet declared war, it was certain that they would, and time was of the essence.
Just when it seemed that the US had come to a decision, though, the European union begged the US to send its forces to Siberia; that way, they could take control of Siberia and begin sending people to start a second front to deal with Russia before moving onto China, leaving the US with no other choice but to comply, because if the European Union began to feel that It couldn't depend on the US, things could truly take a turn for the worst.
With China and Russia both combined, they could not completely lose air superiority, so with a constant supply of new troops to Siberia and the European front, Russia could hold on barely.
As for the Indian front, The US prevented the Chinese from making it past the border, but they couldn't push back yet.
Plus, since it had the biggest oil reserves, the US knew that in a long term war, it would eventually win; it's just that they were in a constant search for a way to save as many American lives as possible; after all, the US although mighty, would still be affected by the populous' opinion, and if too many died, this would become a problem.
Looking at the bigger picture though, and forgetting the war altogether, the US still needed to find a way to secure even more drinkable water, as it was not impervious to climate change and was also having its drinkable water reserves diminish with every passing moment, so after long consideration eventually, the US government did come to a consensus.
Brazil was a US ally, and they had a big majority of the amazon river flow through their territory, so the US was planning to make a deal with Brazil; the deal basically boiled down to the US taking any extra water from the river that Brazil didn't need to keep it's populous alive, and that the Brazilian government would receive more funding and resources from the US.
The deal went really smoothly, and the US set up a system in just a couple of days. The thing was that although the US knew that Peru wouldn't dare to try and dam up the amazon river (because it was impossible in their current situation), it still felt the need to try and make the same deal as they did with Brazil (Probably to get their hands on as much water as possible).
At this point, after learning of the war, I was waiting for the war to be over before I went over to the US to study abroad, mainly because I didn't want to be drafted. Thankfully at the time, Peru, much like most of South America, had been forgotten, and we were able to sit on the sidelines watching everything unfold, just getting ready to bow our heads to whoever won the war.
In a terrible twist of fate though, apparently, the US had somehow looked over just how corrupt the Peruvian government was because they were shocked when the Peruvian government tried to get a better deal than Brazil for just a fraction of the resources, at first the US authorities that it was some twisted joke until they remember just how much of a mess Peru was.
So with the full support of Brazil, the US took control of the Amazon River by 'force,' and there wasn't even an attempt to stop them. Although our leaders were foolish, thankfully, they weren't braindead and could reason that we were nothing more than a bug when put up against the US forces, even counting only those in South America.
This was mainly because, once again, our government was about as corrupt as it could be. They only focused on making themselves richer instead of, you know, helping the populace or investing in the military; hell, they had even sold some of our lands to other countries to make themselves richer.
Thankfully the US was 'merciful' and gave us enough water to make due. The only condition was that we had to sign up to be reinforcements for the forces in India, with the basic job of serving as cannon fodder. Of course, since I didn't have a say in any of this, just like all the others, I too had to bow my head and enlist in the US army.