On 9 August 1942, his orders were abruptly changed.
MacArthur, now Supreme Commander of the Southwest Pacific Area, had requested that a corps headquarters be sent to his command.
Major General Robert C. Richardson, Jr., had originally been detailed for the assignment, but as Marshall informed MacArthur, "Richardson's intense feelings regarding service under Australian command made his assignment appear unwise."
Eichelberger's I Corps headquarters was ready for overseas service and had training in amphibious warfare, and Eichelberger had experience working with MacArthur, so Marshall selected him for the job instead.
Eichelberger was not happy with the assignment, especially when he found out about Richardson, and "knew General MacArthur well enough to know that he was going to be difficult to get along with".

Eichelberger departed for Australia on 20 August with 22 members of his staff in a B-24 Liberator.
I Corps controlled the two American divisions in Australia: Major General Forrest Harding's 32nd Infantry Division, based at Camp Cable near Brisbane; and Major General Horace Fuller's 41st Infantry Division at Rockhampton, Queensland, where Eichelberger, who was promoted to lieutenant general on 21 October, decided to establish his I Corps headquarters.
His I Corps came under the command of Lieutenant General Sir John Lavarack's Australian First Army.
On meeting Australian commanders, Eichelberger noted that many of them "had already been in combat with the British in North Africa, and, though they were usually too polite to say so, considered the Americans to be—at best—inexperienced theorists."
He was disturbed at the level of training received by the two American divisions.
Instead of training for jungle warfare, they were following the same syllabus used in the United States.
He warned MacArthur and MacArthur's chief of staff, Major General Richard K. Sutherland, that the divisions could not be expected to meet veteran Japanese troops on equal terms.
He decided in September that the 32nd Infantry Division should proceed to New Guinea first, as Camp Cable was inferior to the 41st Infantry Division's camp at Rockhampton.

Eichelberger's fears were realized when the overconfident 32nd Infantry Division suffered a serious reverse in the Battle of Buna-Gona.
Harding was confident that he could capture Buna "without too much difficulty", but poor staff work, inaccurate intelligence, inadequate training and, above all, Japanese resistance, frustrated the American efforts.
The Americans found themselves confronted by a network of well-sited and expertly prepared Japanese positions, accessible only through a swamp.
The Americans' failure damaged their relationship with the Australians and threatened to derail MacArthur's entire campaign.
Eichelberger and a small party from I Corps headquarters were hurriedly flown up to Port Moresby in a pair of C-47 Dakotas on 30 November.
MacArthur ordered Eichelberger to assume control of the battle at Buna.
According to Byers and Eichelberger, MacArthur told him "in a grim voice":
"I'm putting you in command at Buna.
Relieve Harding.
I am sending you in, Bob, and I want you to remove all officers who won't fight.
Relieve regimental and battalion commanders; if necessary, put sergeants in charge of battalions and corporals in charge of companies—anyone who will fight.
Time is of the essence; the Japanese may land reinforcements any night."

General MacArthur strode down the breezy veranda again.
He said he had reports that American soldiers were throwing away their weapons and running from the enemy.
Then he stopped short and spoke with emphasis.
He wanted no misunderstandings about my assignment.


"Bob," he said, "I want you to take Buna, or not come back alive."
He paused a moment, and then, without looking at Byers, pointed a finger. "
And that goes for your chief of staff, too."

The next day, Eichelberger's party was flown to Dobodura, where he assumed command of US troops in the Buna area.
He relieved Harding, and replaced him with the division's artillery commander, Brigadier Gener
On 9 August 1942, his orders were abruptly changed. MacArthur, now Supreme Commander of the Southwest Pacific Area, had requested that a corps headquarters be sent to his command. Major General Robert C. Richardson, Jr., had originally been detailed for the assignment, but as Marshall informed MacArthur, "Richardson's intense feelings regarding service under Australian command made his assignment appear unwise." Eichelberger's I Corps headquarters was ready for overseas service and had training in amphibious warfare, and Eichelberger had experience working with MacArthur, so Marshall selected him for the job instead. Eichelberger was not happy with the assignment, especially when he found out about Richardson, and "knew General MacArthur well enough to know that he was going to be difficult to get along with".
Eichelberger departed for Australia on 20 August with 22 members of his staff in a B-24 Liberator. I Corps controlled the two American divisions in Australia: Major General Forrest Harding's 32nd Infantry Division, based at Camp Cable near Brisbane; and Major General Horace Fuller's 41st Infantry Division at Rockhampton, Queensland, where Eichelberger, who was promoted to lieutenant general on 21 October, decided to establish his I Corps headquarters. His I Corps came under the command of Lieutenant General Sir John Lavarack's Australian First Army. On meeting Australian commanders, Eichelberger noted that many of them "had already been in combat with the British in North Africa, and, though they were usually too polite to say so, considered the Americans to be—at best—inexperienced theorists." He was disturbed at the level of training received by the two American divisions. Instead of training for jungle warfare, they were following the same syllabus used in the United States. He warned MacArthur and MacArthur's chief of staff, Major General Richard K. Sutherland, that the divisions could not be expected to meet veteran Japanese troops on equal terms. He decided in September that the 32nd Infantry Division should proceed to New Guinea first, as Camp Cable was inferior to the 41st Infantry Division's camp at Rockhampton.
Eichelberger's fears were realized when the overconfident 32nd Infantry Division suffered a serious reverse in the Battle of Buna-Gona. Harding was confident that he could capture Buna "without too much difficulty", but poor staff work, inaccurate intelligence, inadequate training and, above all, Japanese resistance, frustrated the American efforts. The Americans found themselves confronted by a network of well-sited and expertly prepared Japanese positions, accessible only through a swamp. The Americans' failure damaged their relationship with the Australians and threatened to derail MacArthur's entire campaign. Eichelberger and a small party from I Corps headquarters were hurriedly flown up to Port Moresby in a pair of C-47 Dakotas on 30 November. MacArthur ordered Eichelberger to assume control of the battle at Buna. According to Byers and Eichelberger, MacArthur told him "in a grim voice":
"I'm putting you in command at Buna. Relieve Harding. I am sending you in, Bob, and I want you to remove all officers who won't fight. Relieve regimental and battalion commanders; if necessary, put sergeants in charge of battalions and corporals in charge of companies—anyone who will fight. Time is of the essence; the Japanese may land reinforcements any night."
General MacArthur strode down the breezy veranda again. He said he had reports that American soldiers were throwing away their weapons and running from the enemy. Then he stopped short and spoke with emphasis. He wanted no misunderstandings about my assignment.

"Bob," he said, "I want you to take Buna, or not come back alive." He paused a moment, and then, without looking at Byers, pointed a finger. "And that goes for your chief of staff, too." 
The next day, Eichelberger's party was flown to Dobodura, where he assumed command of US troops in the Buna area. He relieved Harding, and replaced him with the division's artillery commander, Brigadier Gener
Robert L. Eichelberger