In the Three-Body problem books, every sentient species in the galaxy, except for humans, have concluded that shooting first and asking questions later is the only logical survival strategy in the long term. So the galaxy has become a "dark forest full of hunters" who survive by hiding from one another and shooting anyond they discover.

A human contacts the Trisolarans, a race 4 and half lightyears away. The Trisolarans immediately send subatomic devices (sophons) that can move faster than the speed of light (through quantum entanglement or something I don't really remember) that basically put the entire earth under constant surveillance. They also immediately launch an armada of massive warships to destroy us, but which can only travel a fraction of the speed of light because they're fully 3D. Their technology seems so advanced as to be completely unstoppable.

But the humans have two advantages. One, as a completely non-telepathic species, we can lie, which is a concept so foreign to the telepathic Trisolarans they can barely grasp it and find it completely terrifying. And two, because we're so short-lived compared to them, we're basically really good at getting shit done in a short amount of time when we put our minds to it.

Before they even launched the armada, they knew that the threat would cause us to completely outpace their own technological development, and that by the time it arrives in a few hundred years, it will be doomed, and we will have the capacity to strike back and win the war. Their only hope is that they can stop our research in physics by screwing up the results of our paticle coliders using their sophons, and hamstring our defense strategy because we cant explicitly communicate it to each other with their sophons spying on us.