Let’s talk about ideology.
An ideology is a belief or concept that a form of media hopes to propagate as truth, especially relating to how people should live or what they should think. Nausicaa of the Valley of the Wind has a lot to say about humanity, and not all of it is good. The movie may follow an all-loving heroine, but she’s actually a bit of an outlier in her universe. Just look at the neighbors.
The Valley of the Wind is full of people who live simply and in harmony with nature. In fact, it is thanks to the wind from nature that they are protected from the poisons of the nearby Toxic Jungle. They harness the wind to draw well water, which they put toward their crops, but beyond this they do no more harm to the world than the world does to them. They are the only agricultural nation introduced in the film–the other two, Tolmekia and Pejite, are industrial. Incidentally, these two are the ones that start the war making up the plot of the movie–and for the both of them, the end result is destruction, death, and exactly no endgame advantage to make the cost worthwhile. What’s the moral here? If it’s not obvious yet, the backstory for the plot should make it so: one thousand years earlier, industrial society was destroyed by Giant Warriors. The Warriors were creatures that came out of the earth, and they razed all of humanity’s progress because it did too much harm to nature. The nature of the Toxic Jungle, in fact, is the result of the plants drawing out all of the pollutants humankind put into the soil, and purifying it so that new life could grow.
Nausicaa is trying to say that harmony with nature is the only way for humanity to survive without struggle. Especially since it seems nature will stop at nothing to destroy people once and for all if they do damage to the planet again. The Giant Warriors were very much the reset button when the people stopped caring, but even with them at rest and dormant, the toxicity of the plants and the easy provocation of the giant insects have taken their place. If humans harm the bugs, they will stampede until their own death in retaliation.
What else does it say people should do for their own good? Not waging wars would be a step in the right direction. But what if a cause is justified?
The movie would argue no cause is righteous enough for picking a fight with someone else. Tolmekia is the prime example of a nation looking to build an empire; they capture a different kingdom’s princess as an attempt at leverage, occupy the Valley with their military, and attempt to restore one of the Giant Warriors to use as their own ultimate weapon. They do not succeed with the latter, but the kidnapping attempt ends in the princess’ death and draws another into war. The princess came from Pejite, and Pejite plans an attack in retaliation–and once again the occupied Valley is collateral. At the end of the big clash between them (which ends with a giant stampede of angry bugs crashing through the Valley) no one has gained anything, lives have been lost, and destruction is everywhere. No matter the reason any side had for war, no good came of it, and no good ever will–at least, according to the movie.