Former Arsenal striker Henry played under Guardiola during his spell in La Liga with Barcelona and knows first-hand how the coach operates at the helm.
City have confirmed the Bayern Munich boss will take over from Manuel Pellegrini when his contract at the Bundesliga giants expires in June and Henry believes Guardiola will be prepared to make an immediate impact when he takes over control.
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"There is no doubt Guardiola will be making a lot of changes as soon as he arrives," the ex-French international wrote in his article for the Sun.
"He will know the minute he walks into the Etihad who is surplus to requirements.
"And if you don’t fit the bill, you’re out. It doesn’t matter how much you cost, how much you get paid or what you have achieved in the past.
"No one is safe."
Henry, 38, believes Guardiola's determined mindset could enable two-time Premier League champions City to take a firm grip of the division for years to come.
"He is not coming to England just to win the Premier League. He is also coming to dominate it," he continued. "And that’s a terrifying prospect for all of City’s title rivals.
"When he was appointed at Barca, people thought it wasn’t possible for them to get any better.
"But he took them to another level, playing an incredible style of winning football."