Havana, Cuba -- Wearing his signature olive green fatigues, former Cuban President Fidel Castro made his first institutional appearance in four years Saturday, addressing a special session of the communist nation's National Assembly.

Castro had kept out of sight while he recuperated from a life-threatening intestinal illness that required several surgeries and sparked rumors that he was close to death.

Those in the chamber, including his brother and current President Raul Castro, gave the aging revolutionary leader a loud round of applause as he walked in. Even the international media was allowed to listen in as Castro spoke about the dangers of nuclear war, exhorting U.S. President Barack Obama not to fire the first shot in a confrontation.

Castro appeared old but healthy Saturday.

He had temporarily ceded power to Raul Castro in July 2006 and resigned as president in February 2008. He wrote a column called "Reflections" while recuperating and sometimes would be seen in photos when a foreign dignitary like Venezuelan President Hugo Chavez would visit.

But that was all. He was mostly out of sight, if not forgotten.

That reclusive lifestyle ended in mid-July, when photographs of Castro visiting the National Center of Scientific Investigations surfaced on a pro-government blog. A few days later, Castro appeared on a Cuban TV show called "Roundtable."

Since then, he has made several public appearances, including at an unveiling ceremony for his latest book, "The Strategic Victory."

Castro, who turns 84 on August 13, called the National Assembly into special session, which is discussing global affairs, in particular what Castro views as an imminent nuclear war involving the United States, Iran and North Korea. Castro has dwelt on that topic since resurfacing last month.

CNN's Shasta Darlington contributed to this report.