Operation Deep Freeze (OpDFrz or ODF) is the codename for a series of United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 missions to Antarctica, beginning with "Operation Deep Freeze I" in 1955–56, followed by "Operation Deep Freeze II", "Operation Deep Freeze III", and so on. Given the continuing and constant US presence in Antarctica since that date, "Operation Deep Freeze" has come to be used as a general term for US operations in that continent, and in particular for the regular missions to resupply US Antarctic bases, coordinated by the United States military

Military of the United States

The United States Armed Forces are the military forces of the United States. They consist of the Army, Navy, Marine Corps, Air Force, and Coast Guard.The United States has a strong tradition of civilian control of the military...

.
The impetus behind Operation Deep Freeze I was the International Geophysical Year

International Geophysical Year

The International Geophysical Year was an international scientific project that lasted from July 1, 1957, to December 31, 1958. It marked the end of a long period during the Cold War when scientific interchange between East and West was seriously interrupted...

 1957–58.