Why are the three superpowers always at war according to the Brotherhood's handbook? The doublethink concepts of "ignorance and strength" and "war is peace" are discussed in the book of the Brotherhood. Briefly explain the argument of the doublethink concepts. Discuss why the Party's conclusions are ironic. Who is the book written for?

The "Book," The Theory and Practice of Oligarchical Collectivism by Emmanuel Goldstein, is not really a handbook for the Brotherhood. At least, if we are to believe O'Brien, he (and others) produced the book, though much of it seems to tell the exact truth about the Party's lies and its manipulation of the people to further its agenda of power. The basic reason for perpetual war is that it is a form of mass mind control. The Party uses the fact (or the ruse) of an enemy power to frighten its own people and to channel their aggression away from the Party itself. War ties into the doublethink concept because, if "war is peace," then war would be a good thing and not something to be avoided. The Party wants people to believe that the actually negative factors of life in Oceania are positive things that should be welcomed and approved of. If "ignorance is strength," then it's preferable not to know anything, and if "freedom is slavery," then the obvious lack of freedom in this dystopian world, which should be obvious to the average person, is good, and it would be counter-productive to rebel against the Party in order to obtain freedom. These self-contradictory phrases are a negation of the normal thought processes of human beings.
The negation of normal thought is the deeper, underlying reason for the slogans and the general concept of doublethink. The aim of the Party is to destroy the human ability to reason and to draw logical conclusions from the outside world. If one can believe something that is a direct self-contradiction, in which opposites like war and peace are equated, then one's ability to think and to deal with objective reality has been destroyed. This, in fact, is the object of all totalitarian governments, including the actual ones that have existed throughout history—to prevent people from recognizing objective truth and instead to make them believe that "truth" is whatever the Party declares it to be. The ongoing, perpetual war gives the Party the opportunity to test, or to reinforce, this aim. In the scene where Winston is attending a rally and it is abruptly declared that Oceania is at war with Eastasia, not Eurasia, and has always been at war with Eastasia—contrary to what Winston and presumably others remember and know to be the truth—we see the most extreme form of this mind control or manipulation. "Truth is not truth," and what would be (and has been) more benignly described as "alternative facts" becomes reality in a self-created fantasy world of dictatorial rule.