The rationalizations made by IngSoc in "1984" were different than what bitter_engineer believes them to be.
War is Peace: You have to understand that in the novel "1984", there were three major powers of the world. Eurasia, Eastasia, and Oceania. At all times, two of the three powers were allied against the third. This resulted in a state of perpetual war, and though it allowed for a state that rounded up "dissenters", that was not the main reason for perpetual war. The reason war was a constant was that war had become peace.
In the past, every war had been fought for political gain or new resources. In a world of three dictatorships, each with enough resources to sustain themselves indefinitely, there was no longer any need to wage a real war with real consequences. What was needed was a way to throw away resources and gain small victories which could be touted to the public as grand changes for the better. The resources were being thrown away so the people would have a constant need for a government, even one that was repressing them. Thus, by fighting this grand war on their borders, they were actually guaranting peace within those borders.
All the wars in "1984" were actually small affairs, involving less then 1% of the nations resources, and even less men. In fact, the three nations had already realized the only winning move was to completely surround an enemy nation and nuke it out of existence in one grand move, something that could no longer be achieved.
Freedom is Slavery: The argument behind "Freedom is Slavery" is a simple one. How can one man build a bridge, a skyscraper, or anything large on their own? The simple answer is that one alone cannot build these things without help. Thus the individual is powerless, and individual freedom weakens the individual by making it impossible to do anything grand. Therefore, to do anything grand, a person must join up with others and suppress their own will and personal freedoms. Otherwise, they achieve nothing, and destroy any attempt to achieve anything by doing so. The only true freedom a person has is the freedom to submit to a larger group and to influence that group by helping it. Therefore, freedom is slavery.
Ignorance is Power: In the world of "1984", to be called "black-white" was both a compliment and an insult. As a compliment, it meant that one could see everything black as being white if and when it was necessary and vice-versa. As an insult, it meant that a person was so stupid as to see something that was clearly black, as white. In effect, it was good to be ignorant of the facts, and bad to be ignorant of the current political spectrum. Ignorance had become powerful, whether it existed in you or your enemies, it could be used by for your own gain. Ignorance is Power.