Rewrite each original sentence in order to make it easier to understand by non-native speakers of English. You can do so by replacing complex words with simpler synonyms (i.e. paraphrasing), deleting unimportant information (i.e. compression), and/or splitting a long complex sentence into several simpler ones. The final simplified sentences need to be grammatical, fluent, and retain the main ideas of their original counterparts without altering their meanings.

Rawalpindi is also the military headquarters of the Pakistan Armed Forces and also served as the nation's capital while Islamabad was being constructed in the 1960s.

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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Rawalpindi is the base of the Pakistan Armed Forces. It also was a capital while Islamabad was being built.