Please explain the following passage from 1984:
"War, it will be seen, accomplishes the necessary destruction, but accomplishes it in a psychologically acceptable way. In principle it would be quite simple to waste the surplus labour of the world by building temples and pyramids, by digging holes and filling them up again, or even by producing vast quantities of goods and then setting fire to them. But this would provide only the economic and not the emotional basis for a hierarchical society. What is concerned here is not the morale of masses, whose attitude is unimportant so long as they are kept steadily at work, but the morale of the Party itself. Even the humblest Party member is expected to be competent, industrious, and even intelligent within narrow limits, but it is also necessary that he should be a credulous and ignorant fanatic whose prevailing moods are fear, hatred, adulation, and orgiastic triumph. In other words it is necessary that he should have the mentality appropriate to a state of war. It does not matter whether the war is actually happening, and, since no decisive victory is possible, it does not matter whether the war is going well or badly. All that is needed is that a state of war should exist. The splitting of the intelligence which the Party requires of its members, and which is more easily achieved in an atmosphere of war, is now almost universal, but the higher up the ranks one goes, the more marked it becomes. It is precisely in the Inner Party that war hysteria and hatred of the enemy are strongest. In his capacity as an administrator, it is often necessary for a member of the Inner Party to know that this or that item of war news is untruthful, and he may often be aware that the entire war is spurious and is either not happening or is being waged for purposes quite other than the declared ones: but such knowledge is easily neutralized by the technique of doublethink.
Meanwhile no Inner Party member wavers for an instant in his mystical belief that the war is real, and that it is bound to end victoriously, with Oceania the undisputed master of the entire world."
This passage is important because it explains part of the rationale behind why Oceania is the way that it is, and why the war is so important a part of the way in which the Party maintains control of its people and keeps them so focussed on the war and an enemy (whoever that enemy is) that they do not have enough energy, intelligence or will to rebel against the Party itself. Note the way that the war is referred to as being superfluous in terms of its details:
It does not matter whether the war is actually happening, and, since no decisive victory is possible, it does not matter whether the war is going well or badly. All that is needed is that a state of war should exist.
Key things to note are the adjectives applied to war: "spurious," and "untruthful." As with so many other factors in this dystopian text, the actual truth of the matter is actually unimportant. What is massively important is the appearance and how things are perceived. The details of the enemy and how the war is going are just side issues, as is shown when Winston and the rest of the Ministry of Truth have to work very hard to change history when Oceania switches enemies. The quote finally concludes by suggesting that the fervent belief in war is strongest with the Inner Party, even though those are precisely the people who will have evidence about the non-existence of the war or some of the details provided. The quote describes the belief in war as a kind of mass hysteria where so many willingly believe in something that they may doubt to actually exist. This is yet another example of the power of the Party as they seek to create their own version of truth and reality that is more important than actual truth and reality.