The plans for the invasion of Borneo evolved considerably during April. Initially, the offensive was to commence on 23 April with the landing of a brigade from the 6th Division on the island of Tarakan, off the east coast of Borneo. The 9th Division would then assault Balikpapan followed by Banjarmasin in south-east Borneo. These positions would be used to support the invasion of Java by the remainder of I Corps. After the attack on Java was cancelled, it was decided to employ two brigades of the 7th Division at Brunei Bay, and I Corps conducted further preparations on this basis. However, on 17 April General Douglas MacArthur's General Headquarters (to which I Corps reported) swapped the roles of the 7th and 9th Divisions. Accordingly, the final plan for the attack against Borneo specified that one of the 9th Division's brigades would land on Tarakan island on 29 April (later postponed to 1 May), with the remainder of the division to invade the Brunei Bay area on 23 May. The 7th Division was scheduled to assault Balikpapan on 1 July. The Borneo campaign was designated the "Oboe" phase of the Allied offensive through the southern Philippines towards the Netherlands East Indies, and the landings at Tarakan, Brunei Bay and Balikpapan were designated Operations Oboe One, Six and Two respectively.