Paris - President Francois Hollande said in his New Year's Eve address to the nation on Thursday that France "has not finished with terrorism yet".
Speaking six weeks after gunmen and suicide bombers killed 130 people in Paris, Hollande said the threat of another attack "remains at its highest level".
After a "terrible" year in which jihadists also attacked the satirical newspaper Charlie Hebdo, a Jewish supermarket and a heavily armed man attacked passengers on a high-speed train in France, Hollande said his "first duty" was to protect the French people.
"That means attacking the root of the evil...in Syria and Iraq. That is why we have intensified our air strikes against Daesh," he said, using another name for the Islamic State (ISIS) group.
Hollande said ISIS was feeling the hit from the assault.
"The hits are taking their toll...the jihadists are in retreat, so we will continue as long as necessary," he added.
Hollande said he was "proud" of the French people for showing "solidarity and cool-headedness" after the attacks in January and in the wake of the carnage on November 13.
"Despite this tragedy, France did not give in," Hollande said. "Despite the tears, it remained upright. Confronted by hate, it showed the strength of its values, the values of the Republic."
The president was defiant on his plans to strip dual nationals who are convicted of terrorist offences of their French nationality.
He said while it was "legitimate" to have a debate about the proposal that has deeply divided his Socialist party, "when it comes to your protection, France must not be divided".
More than 100 000 police are on duty across France for the New Year's Eve celebrations, including 11 000 in Paris where the main fireworks display has been cancelled this year.