Newspeak plays an extremely important role in Oceanian society and in the Party's control over its population. As Syme says, Newspeak reduces and limits the number of words in the English language, and removes words used to describe rebellion or independence (with the ultimate goal being to remove citizens' ability to think anti-Party thoughts). Interestingly, the Party works to form a language around itself rather than naturally accepting and assuming the language of the people that make up the country. In this way, language is used as yet another mechanism of mind control.
Removing a nation's original language serves to reduce the importance of a nation's past. Languages develop over centuries, and are deeply intertwined with culture and history. Redefining and forcing a language on a population, as was often done in the postcolonial era, denies that society its individuality. The Party meets this goal with great efficiency.