For a fission bomb yes, not s fusion (thermonuclear/hydrogen) bomb.
Fire bombing can (and has done) more damage to a city than a fission bomb.
Fire bombing can (and has done) more damage to a city than a fission bomb.
Mass arson is possible, though not on the scale of firebombing. The US in WWII developed the idea of strapping incendiary bombs on bats and releasing them in a city, where they would roost in random buildings and start hundreds of small fires.