A covert CIA operation in Yemen intercepted an 'undetectable' bomb intended to blow up an airplane. Authorities suspect it was the work of master bomb maker Ibrahim Hassan al-Asiri. Al-Asiri, who built the first underwear bomb.
Officials said the plot, timed to occur about a year after the death of Osama bin Laden, involved a more advanced version of the underwear bomb that failed to detonate on a plane over Detroit in December 2009.
During his presidency, Barack Obama has undertaken a string of military operations, topped by the raid that killed Osama bin Laden hiding in Pakistan. One expert calls Obama 'one of the most militarily aggressive American leaders in decades.'