An ailing, 81-year-old Fidel Castro resigned as Cuba's president Tuesday after nearly a half-century in power, saying he will not accept a new term when parliament meets Sunday.

The end of Castro's rule _ the longest in the world for a head of government _ frees his 76-year-old brother Raul to implement reforms he has hinted at since taking over as acting president when Fidel Castro fell ill in July 2006. President Bush said he hopes the resignation signals the beginning of a democratic transition.

Keep reading about the details here.

President Bush spoke about Castro and the future of Cuba while on his trip through Africa:

President Bush, asked about the news in a public appearance during his trip to Africa, said "the question really should be what does this mean for the people in Cuba. They are the ones who suffered under Fidel Castro."

Bush said he hoped this would be "the beginning of a democratic transition for the people of Cuba . . . An interesting debate will arise. Some will say let's promote stability. In the meantime, political prisoners will rot . . . This should be a transition to free and fair elections. And I mean free and fair. Not these elections that the Castro brothers rig."

Watch Bush's statement as well as reaction from Miami.

Hillary Clinton released a statement on Castro's resignation:

"As you know, Fidel Castro announced that he is stepping down as Cuba's leader after nearly 50 years of one-man rule. The new leadership in Cuba will face a stark choice -- continue with the failed policies of the past that have stifled democratic freedoms and stunted economic growth -- or take a historic step to bring Cuba into the community of democratic nations. The people of Cuba want to seize this opportunity for real change and so must we.

"I would say to the new leadership, the people of the United States are ready to meet you if you move forward towards the path of democracy, with real, substantial reforms. The people of Cuba yearn for the opportunity to get out from under the weight of this authoritarian regime, which has held back 11 million talented and hardworking citizens of the Americas. The new government should take this opportunity to release political prisoners and to take serious steps towards democracy that give their people a real voice in their government.

Read the full text of Clinton's statement here.

Barack Obama released a statement on Castro's resignation:

"Today should mark the end of a dark era in Cuba's history. Fidel Castro's stepping down is an essential first step, but it is sadly insufficient in bringing freedom to Cuba.

"Cuba's future should be determined by the Cuban people and not by an anti-democratic successor regime. The prompt release of all prisoners of conscience wrongly jailed for standing up for the basic freedoms too long denied to the Cuban people would mark an important break with the past. It's time for these heroes to be released.

"If the Cuban leadership begins opening Cuba to meaningful democratic change, the United States must be prepared to begin taking steps to normalize relations and to ease the embargo of the last five decades. The freedom of the Cuban people is a cause that should bring the Americans together."

John McCain, R-Ariz., also issued a written reaction to the media.

"Today's resignation of Fidel Castro is nearly half a century overdue. For decades, Castro oversaw an apparatus of repression that denied liberty to the people who suffered under his dictatorship.

"Yet freedom for the Cuban people is not yet at hand, and the Castro brothers clearly intend to maintain their grip on power. That is why we must press the Cuban regime to release all political prisoners unconditionally, to legalize all political parties, labor unions and free media, and to schedule internationally monitored elections.

"Cuba's transition to democracy is inevitable; it is a matter of when -- not if. With the resignation of Fidel Castro, the Cuban people have an opportunity to move forward and continue pushing for the moment that they will truly be free. America can and should help hasten the sparking of freedom in Cuba. The Cuban people have waited long enough."

Castro's successor is his brother youngest brother Raul, the man who has been the de facto ruler of Cuba since 2006.

Who is Raul Castro? According to Wkipedia:

Raul Modesto Castro Ruz (born June 3, 1931) is the President of Cuba and Acting President/First Vice President of the Cuban Council of State. The younger brother of former Cuban President Fidel Castro also occupies the positions of First Vice President/Acting President of the Council of Ministers, Acting First Secretary/Second Secretary of the Politburo of the Central Committee of the Communist Party of Cuba (PCC), and Acting Commander in Chief Maximum General of the Armed Forces (Army, Navy, and Air Force), second only to the Commander in Chief, Fidel Castro.

Raul Castro fought alongside his brother in the 1953 assault on the Moncada barracks. He was jailed, along with Fidel, for 22 months. It is Raul who is said to have befriended Che Guevara and introduced him to Fidel. In 1959 the Castro brothers, Guevara and their guerilla army returned to Cuba and overthrew Fulgencio Batista's government in 1959. Older brother Fidel assumed leadership and officially ruled until today.

Below is a photo of Fidel and Raul Castro taken in July 2004.