These words are the official slogans of the Party, and are inscribed in massive letters on the white pyramid of the Ministry of Truth, as Winston observes in Book One, Chapter I. Because it is introduced so early in the novel, this creed serves as the reader’s first introduction to the idea of doublethink. By weakening the independence and strength of individuals’ minds and forcing them to live in a constant state of propaganda-induced fear, the Party is able to force its subjects to accept anything it decrees, even if it is entirely illogical—for instance, the Ministry of Peace is in charge of waging war, the Ministry of Love is in charge of political torture, and the Ministry of Truth is in charge of doctoring history books to reflect the Party’s ideology.

That the national slogan of Oceania is equally contradictory is an important testament to the power of the Party’s mass campaign of psychological control. In theory, the Party is able to maintain that “War Is Peace” because having a common enemy keeps the people of Oceania united. “Freedom Is Slavery” because, according to the Party, the man who is independent is doomed to fail. By the same token, “Slavery Is Freedom,” because the man subjected to the collective will is free from danger and want. “Ignorance Is Strength” because the inability of the people to recognize these contradictions cements the power of the authoritarian regime.

THE VEIL
This Party slogan appears twice in the novel, once in Book One, Chapter III, when Winston is thinking about the Party’s control of history and memory, and once in Book Three, Chapter II, when Winston, now a prisoner in the Ministry of Love, talks to O’Brien about the nature of the past. The slogan is an important example of the Party’s technique of using false history to break down the psychological independence of its subjects.
TONE
The phrasing creates an ominous tone that foretells of psychological and historical control of the party. Control of the past ensures control of the future, because the past can be treated essentially as a set of conditions that justify or encourage future goals: if the past was idyllic, then people will act to re-create it; if the past was nightmarish, then people will act to prevent such circumstances from recurring. The Party creates a past that was a time of misery and slavery from which it claims to have liberated the human race, thus compelling people to work toward the Party’s goals.The Party has complete political power in the present, enabling it to control the way in which its subjects think about and interpret the past: every history book reflects Party ideology, and individuals are forbidden from keeping mementos of their own pasts, such as photographs and documents. As a result, the citizens of Oceania have a very short, fuzzy memory, and are willing to believe anything that the Party tells them. In the second appearance of this quote, O’Brien tells Winston that the past has no concrete existence and that it is real only in the minds of human beings. O’Brien is essentially arguing that because the Party’s version of the past is what people believe, that past, though it has no basis in real events, has become the truth.

Tools of Satire: Aphorism
The repetition of Who controls creates a rhythmic beat of power. This repetition reinforces the power and control that occurs in action of the story: the repetition of language mirrors the overwhelming feeling of oppression the idea illustrates.

The Target

The target is Stalin's media apparatus that regularly re-wrote the past to suit their needs. Most famously after Stalin had Trotsky assassinated he then had his media experts erase Trotsky from all public records.