Впоследствии властям потребовалось

Впоследствии властям потребовалось 6 недель на то, чтобы убедить население в том, что нападения не происходило.

Результаты (английский) 1:

Subsequently, the authorities took 6 weeks to convince the population that the attack did not occur.

Результаты (английский) 2:

Subsequently, the authorities took 6 weeks to convince the population that the attack happened.

Результаты (английский) 3:

Subsequently, it took the authorities 6 weeks, to convince the population of the fact that the attacks would not have happened.