But there are limits, even to this new president's power, and a campaign pledge to seek a ban on assault weapons is an early casualty as a result.
And while the promise of change was arguably Obama's single most powerful asset in last year's campaign, the week demonstrated anew how carefully he calibrates its impact.
"We have been through a dark and painful chapter in our history," the president said in a statement that accompanied the release of once-secret memos outlining torture techniques the Bush administration allowed.
"But at a time of great challenges and disturbing disunity, nothing will be gained by spending our time and energy laying blame for the past."
That was designed as a reassurance to the CIA employees who carried out waterboarding, which simulates drowning, and the other harsh interrogation techniques that former President George W. Bush once sanctioned and that Obama has now banned
- much as his decision to leave combat troops in Iraq a few months longer than he once promised was a bow to the Pentagon.
"I will always do whatever is necessary to protect the national security of the United States," he said in a statement on the torture memos that could easily have been written about the troop withdrawal.
Attorney General Eric Holder added one more assurance, announcing the administration would pay legal expenses for anyone in the intelligence agency who needs a lawyer as a result of carrying out interrogations covered by the memos.
Holder also formally revoked every legal opinion or memo issued during Bush's presidency that justified interrogation programs, a largely symbolic step since Obama had already said his administration would not rely on them.
The release of the documents had been the subject of a long, fierce debate, with a deadline looming as the result of a lawsuit brought by the American Civil Liberties Union.
No lawsuit drove the timing of the new Cuba policy, which was released in the run-up to Obama's first presidential trip to Central America. And here again, Obama went further than some wanted and not as far as others had hoped.
Under the new policy, the administration lifted restrictions on Cuban-Americans who want to travel and send money to their island homeland and freed U.S. telecommunications companies to seek business there.
Some of the changes specifically undid what Bush had imposed: tightened travel restrictions on Americans wishing to visit relatives in Cuba; limiting payments to immediate family; and bans on seeds, clothing, personal hygiene items, veterinary medicines and
- later - cell phones from humanitarian parcels.
But the broader embargo remains in place as it has since the Kennedy administration, its existence meant now as then to prod the Cuban government into democratic reforms.
In response to the announcement, Cuban President Raul Castro said he is ready to put "everything" on the table in talks with Americans, including questions of human rights and political prisoners. If so, that would mark a change from decades of Cuban insistence that those issues were not subject for discussion.
Secretary of State Hillary Rodham Clinton pronounced Castro's comments an overture, and said, "We are taking a very serious look at how we intend to respond."