"South Korean and USA air forces showed off the allies' resolve for strong retaliation against North Korea's nuclear and missile threats", the JCS said in a statement carried by local news agency Yonhap.
Late last month, the U.S. flew B-1Bs over worldwide waters close to the North's east coast.
The four aircraft then flew across the peninsula and staged another round of a firing exercise over the Yellow Sea before the two B-IBs returned home, the South Korean Joint Chiefs of Staff (JCS) said. Such flights by the powerful aircraft based in Guam incense the North, which claims they are preparation for war; Pyongyang has threatened to send missiles into the waters around Guam.
The show of force happened Tuesday as President Donald Trump met with his national security team to discuss options for dealing with the growing threat from the North.
News of the hack is likely to further fuel tensions between the U.S. and North Korea, as leaders of the two countries have been exchanging insults over Pyongyang's recent missile tests.
The US bombers had taken off from the Andersen Air Force Base in Guam.
President Trump hosted a discussion on options to respond to any North Korean aggression, or, if necessary, to prevent Pyongyang from threatening the U.S. and its allies with nuclear weapons, the White House said in a statement.
The stolen money was likely used to help advance North Korea's development of nuclear weapons, Anthony Ruggiero, a senior fellow for Foundation for Defense of Democracies, told CNN at the time. Kim is the third generation of his family to rule North Korea.
Lee said that 235 gigabytes of military documents were taken, but the military has yet to identify 80 percent of the documents that were compromised.
According to South Korea's Yonhap news agency this is not the first time the communist regime to the north has launched a tirade of cyber attacks on the country, with hacks targeting government websites and facilities being commonplace in recent years.
"The operations plan that they are referring to is a bilateral plan, so the Republic of Korea-US alliance remains steadfast in their commitment to make sure they safeguard that information and ensure readiness on the Korean peninsula to counter any North Korean threats", Manning said.