Hours after a surprise return from Cuba Monday, Venezuelan President Hugo Chavez rallied a crowd of thousands of supporters Monday night, vowing to win a “battle for life” after undergoing cancer surgery.

Chavez addressed the crowd from a balcony of the presidential palace.

The Venezuelan president thanked Fidel Castro, saying that the veteran leader has been practically his “medical chief” while recovering in Cuba.

Chavez spoke strongly but was thinner and paler than usual. He wore the red beret from his days as an army paratroop commander.

Chavez said he spent “very difficult days” in Cuba but that his recovery is going well. “It’s the beginning of my return!”

NPR’s Juan Forero, in Caracas, says the surprise return is likely intended to demonstrate that “Chavez is still in charge” after his absence left a vacuum in Venezuela.

“He’s always on TV. He’s omnipresent here in Venezuela and the government really revolves around him,” Forero said on All Things Considered. “This is a way for the government to show that Chavez is getting better and getting better fast.”

Forero said: “Remember, Chavez has a mystical connection with his people … He’s held up by some here as a messiah who has delivered his people from the clutches of the oligarchs and the gringos — meaning the United States.

“So he can’t get sick. It can’t appear that he’s weak.”

The return will likely have a quick impact on political rivals, Forero said.

“Some allies of the government are already attacking the opposition,” he said. “Some of those opposition politicians had demanded that the government transfer power to the vice president. I suspect they’ll be made to pay for that — for those comments.”

Next year is a presidential election year for Venezuela and Forero said the revelation that the president is battling cancer is particularly jarring.

“For many Venezuelans, it just goes to show how vital Chavez is to the state,” Forero said. “Many people are worried about how he has been made this icon who cannot be replaced.”

Chavez arrived a day before the 200th anniversary of Venezuela’s declaration of independence from Spain.

He had been in Cuba since June 8 for what ostensibly was a previously scheduled visit. Doctors said he underwent an initial surgery on June 11 to have a pelvic abscess removed and then a follow-up surgery to remove a cancerous “abscessed tumor” from his pelvic region.

Chavez announced the second surgery Thursday after 18 days out of sight. Neither he nor doctors gave details about what kind of cancer it is or what treatment he is receiving.

Material from The Associated Press is included in this report.

Copyright 2011 National Public Radio. To see more, visit http://www.npr.org/.