The plane crossed stealthily into Belarussian airspace and headed for the capital, Minsk. At the appointed moment, the cargo doors opened, and an invasion force of tiny plush freedom fighters parachuted to the ground.

Belarus was under attack — by teddy bears.

Three members of a Swedish advertising firm planned and carried out the operation last month, adorning more than 800 plush bears with signs promoting democracy and denigrating Belarus’s authoritarian government.

Comedic touches aside, the security breach has become a major embarrassment for President Aleksandr G. Lukashenko, who has channeled his country’s meager resources into maintaining a calcified police state.

Though the government at first tried to cover up the incident, which occurred on July 4, the many photographs and videos of the bear drop uploaded to the Internet made it impossible to ignore. On Tuesday, Mr. Lukashenko fired two generals: the head of the border service and the head of the air force.