Mr. Hollande deployed 10,000 soldiers on the streets of Paris and other cities the day after the attacks. Their force is likely to grow as the government reverses an earlier budget-cutting plan to reduce the size of the military in coming years.

French military spending, which reached 42 billion euros, or more than $52 billion, last year for military operations, weapons, surveillance networks and other support, will grow by €600 million next year to finance the new positions and necessary equipment, Finance Minister Michel Sapin said last week.

The French Army, currently the largest in Western Europe, will take on an additional 10,000 recruits this year and 15,000 more next year. The French national police force and gendarmerie will expand by about 5,000 members, along with 1,000 new customs inspection positions and 2,500 at the French Ministry of Justice.

The ranks of the military reserves will also deepen. Renan Massiaux, a banker, said in an interview that he was “hurt and angry about the attacks.” At age 32, he was older than the cutoff of age 29 for becoming a soldier, but he hoped to be able to “protect France even as a reservist,” he said.

The rather un-French impulse to overtly embrace patriotism has spread in other ways. The singing of “La Marseillaise” has been breaking out spontaneously at sports events, on the streets and even at some business meetings.

And while the French insist that American-style flag waving is not part of their culture, people have been flocking to snap up the French “tricolore.” Hervé Burg, the president of Paris Drapeaux, a flag maker, said orders had jumped by 400 percent since the attacks. “Before, people bought flags here and there for sports events or other functions,” he said. “But now they want the flag right away. They want to hang it from their balconies instead of keeping it inside. The behavior is really patriotic.”