Meanwhile, the Allied Supreme Commander in the South West Pacific Area, General Douglas MacArthur set about developing airfields for the defence of Port Moresby, and to strike against the Japanese. The first of these, Operation Boston, was authorised on 20 May and initially planned for the Abau–Mullins Harbor area. Milne Bay was subsequently determined to be preferable and a garrison force was sent by ship from Port Moresby on 22 June. Another strip at Merauke, on the south coast of Dutch New Guinea was authorised on 22 June to protect the western flank. On 9 June, MacArthur questioned General Sir Thomas Blamey, the commander of Allied Land Forces, as to measures taken for the defence of the overland approach from Buna. This set in train the deployment of forces to Kokoda. MacArthur began to consider the development of an airfield in the Buna area. An initial reconnaissance, landed by flying boat, was conducted on 10 and 11 July. Orders for the airfield construction, Operation Providence, were received by New Guinea Force (NGF) on 17 July, but were postponed by seven days on 18 July, and cancelled following the Japanese landings that shortly followed.