Operation Buffalo was the first nuclear test series to be conducted at Maralinga, and the largest ever held in Australia. Planning for the series, initially codenamed Theta, began in mid-1954. It was initially scheduled for April and May 1956, but was pushed back to September and October, when meteorological conditions were most favourable. Ultimately all tests on the Australian mainland were conducted at this time of year. The 1954 plan for Operation Theta called for four tests, each with a different purpose.