The Japanese at Ioribaiwa

On 14 September 1942 Japanese infantry attacked Australian positions on Ioribaiwa Ridge in the Owen Stanley Range. This was already on the southern side of the mountains, on one of the last high ridges before the valley in which lay Port Moresby – the main Allied base in New Guinea and the objective of the Japanese overland march along the Kokoda Track. From the peaks around Ioribaiwa, according to many accounts, Japanese soldiers could see the lights of the town at night and the Coral Sea. After seven weeks of jungle fighting that had begun with the landing at Buna and Gona and the capture of Kokoda, Port Moresby seemed within reach.

It is often said that on this day the Japanese were 30 miles, or just under 50 km, from Port Moresby. Sources give the distance differently, depending on how it is measured: in a straight line they were about 30–40 km from the town (some studies say 32 km), and considerably more along the track and the road. Either way, Ioribaiwa proved to be the furthest point reached by the Japanese advance on Port Moresby.

The road to Ioribaiwa

At the end of August the main body of Major General Tomitarō Horii’s South Seas Detachment – above all the 144th and 41st Infantry Regiments – attacked at Isurava. In the fighting of 26–31 August it broke the Australian 21st Brigade of Brigadier Arnold Potts, veterans of the Syrian campaign, together with the militia battalions that had been defending the track since July. The Australians fell back through Eora Creek and Templeton’s Crossing, destroying the stores they could not carry.

In those same days the Australians defeated the Japanese landing at Milne Bay, and on 5 September the Japanese evacuated the survivors from there. This freed the 21st Brigade’s third battalion, the 2/27th, which set off up the track, and Potts, under pressure from superiors who demanded an end to the retreat, decided to give battle on Mission Ridge and Brigade Hill near the village of Efogi. On 8 September a Japanese battalion outflanked his positions by night and came out on the track between brigade headquarters and the forward battalions. The battle, which the historian Nicholas Anderson called a disaster without any mitigating circumstances, cost the Australians, according to Australian figures, 87 killed and 77 wounded, and the Japanese 60 killed and 165 wounded. The 21st Brigade, which had begun the fighting at Isurava about 1,800 strong, was now down to only about 300 men.

Lieutenant General Sydney Rowell, commander of New Guinea Force, recalled Potts to Port Moresby. On 10 September command of the force on the track, known as Maroubra Force, passed to Brigadier Selwyn Porter, with orders to stabilise the situation and regain ground – which, as the Australian historian Peter Brune observes, was impossible in the circumstances and showed how far the headquarters had drifted from the realities of the front. Porter withdrew the remnants of the 21st Brigade through Menari and Nauro – on the way the rearguard laid an ambush in the Maguli Range that inflicted heavy losses on the pursuers – and halted on Ioribaiwa Ridge, the last good position before Imita Ridge.

The battle on the ridge (14–16 September)

Ioribaiwa is a long ridge running across the track south of Ofi Creek, dominated by two high peaks. By 11 September a composite force of the remnants of the 2/14th and 2/16th Battalions, only two companies strong, had taken up positions on the track, on a spur running down to the north, with the militia 3rd Battalion to its right. Commandos of the 2/6th Independent Company covered the flanks. On 12 and 13 September Japanese artillery and mortars shelled the ridge from the opposite slope, and the Australians, having no guns of their own, could reply only by ambushing patrols; in one of these, at an abandoned food dump on Ofi Creek, 20–30 Japanese were killed.

At the same time the fresh 25th Brigade of Brigadier Kenneth Eather arrived from the direction of Port Moresby – the 2/25th, 2/31st and 2/33rd Battalions of the Second Australian Imperial Force, veterans of the fighting in Syria and Lebanon in 1941 who had returned from the Middle East to Australia in the spring of 1942. As the senior officer, Eather took command of the whole force. He was to pass through Porter’s positions and counter-attack on both flanks towards Nauro to cut the Japanese line of communication. According to Australian figures Maroubra Force now numbered 2,957 men, while the Japanese of Colonel Masao Kusunose’s 144th Regiment who took part in the battle numbered about 1,650. Horii’s main body waited in the rear for permission to advance further.

On 14 September the Japanese forestalled the counter-attack. They struck just as the 2/31st and 2/33rd Battalions were moving to their start lines on the flanks. Half of the 3rd Battalion of the 144th Regiment, supported by the fire of a mountain battery, attacked in the centre along the track. The attackers suffered losses from booby traps and small-arms fire, but pushed the combined 2/14th–2/16th Battalion a little to the south; it suffered heavily from Japanese artillery, to which the Australians had no answer. The Japanese 2nd Battalion tried to outflank the defenders from the west and unexpectedly ran into the 2/31st Battalion on a flank it had believed to be empty.

On 15 September the other half of the 3rd Battalion searched for the Australians’ eastern flank. The line proved longer than the Japanese had thought, but they found a gap in it between the 3rd Battalion and the 2/33rd Battalion and surprised a militia section that had posted no sentry while digging in. In this way they took a point from which they could fire on the Australians from the east. A counter-attack by the 2/25th Battalion from reserve failed to dislodge them, but they could not advance any further either. On the western flank the two sides took turns trying to outflank each other, each time without success.

The withdrawal to Imita

On 16 September the fighting reached stalemate. Kusunose was weighing up what to do next: he knew he had fewer men than his opponent and no reserves. Eather did not know his position, but he could see the Japanese wedge on his right flank and mounting losses in the centre. He concluded that he could not hold the ridge and that it was unsuitable for a counter-attack. After consulting Porter he asked for permission to withdraw to Imita Ridge, the last position before the start of the track. The commander of the 7th Division, Major General Arthur Allen, agreed on one condition: there would be no further retreat from Imita, and the ridge must be held at all costs. The Australians crossed Ua-Ule Creek and by the morning of 17 September had occupied Imita. There, for the first time in the campaign, they found themselves within range of their own artillery: two 25-pounder guns of the 14th Field Regiment had been hauled by hand to the top near Uberi.

Losses at Ioribaiwa were similar on both sides. According to Australian figures the Australians lost 49 killed and 121 wounded, most of them to Japanese artillery fire; the Japanese lost about 40 killed and 120 wounded. The historian Peter Williams believes that Eather withdrew unnecessarily, since it was the Japanese who were stuck, and sums up: “Eather came to believe that he had been beaten – and so he was.” Others point out that for the first time in the campaign the Australians had halted a Japanese attack before they themselves pulled back.

Why the Japanese went no further

The Japanese occupied the abandoned ridge on 16 September, cheering at the sight of the sea. They did not, however, attack Imita. The South Seas Detachment was at the end of its strength. It had set out from Kokoda with food for sixteen days, and the march had now lasted more than forty-five. Its supply line stretched across the mountains all the way to the coast near Buna; supplies were carried by porters and soldiers, while Allied aircraft bombed bridges and dumps. At Ioribaiwa the daily rice ration was cut to about 180 millilitres per soldier, and malaria and dysentery came on top of hunger.

Even more important were orders from above. From the end of August Lieutenant General Harukichi Hyakutake’s 17th Army and the General Staff in Tokyo had been instructing Horii to go no further than the southern slopes of the mountains and to keep his main body on their northern side; on 8 September the 17th Army ordered him to concentrate the 41st Regiment in the Kokoda area. According to the Japanese official history, Horii did withdraw his main body but allowed his vanguard to continue. On Guadalcanal, meanwhile, the US Marines held Henderson Field, repulsing the attack of Major General Kiyotake Kawaguchi’s force on the nights of 12–13 and 13–14 September in the Battle of Bloody Ridge. When news of this defeat reached Tokyo, Imperial General Headquarters concluded that it could not conduct two offensives at once. On the Allied side, MacArthur and Blamey knew only that the Japanese stood a few dozen kilometres from Port Moresby.

Closest to Port Moresby

The following days showed how much alarm Ioribaiwa caused in Port Moresby, Brisbane and Canberra. On 9 September the Minister for the Army, Frank Forde, had instructed General Thomas Blamey, commander of the Allied land forces, to check the situation on the spot; Blamey was in Port Moresby from 12 to 14 September and assured the government that he had confidence in Rowell. General Douglas MacArthur thought otherwise. He persuaded the Prime Minister, John Curtin, to send Blamey to New Guinea and order him to take personal command; Blamey flew in on 23 September, which soon led to Rowell’s dismissal. From mid-September MacArthur was also moving the first regiments of the US 32nd Infantry Division to Port Moresby, largely by air.

The Japanese attack, however, never came. On 19 September Hyakutake, having learned of the capture of Ioribaiwa, issued a strict order for the leading units to fall back to positions north of Mawai, and on 23 September he ordered the Isurava and Kokoda area to be fortified as a base for future operations. Meanwhile Australian patrols from Imita harassed the Japanese on the ridge, and from 20 September the 25-pounders shelled them. On 24 September the 2nd Battalion of the 144th Regiment left Ioribaiwa, followed on the night of 25–26 September by the Japanese rearguard. When the 25th Brigade advanced on 28 September, it found the trenches empty.

Place in the war

Ioribaiwa was the southernmost point of the Japanese overland advance on Port Moresby, and also the last of the Australians’ defensive battles on the Kokoda Track. Since the spring of 1942 the Japanese had tried to take the base by various routes: from the sea, which was thwarted by the Battle of the Coral Sea, across the mountains, and via Milne Bay. All these attempts had ended in defeat by September. From then on Port Moresby was to be for the Allies not a threatened foothold but a base for the offensive.

In October the Australians set off in pursuit along the track they had earlier travelled in retreat, and after heavy fighting at Eora Creek and Templeton’s Crossing they retook Kokoda on 2 November. Horii died in November when, during the retreat, he tried to travel down the swollen Kumusi River to the coast, first by raft and then by canoe; the current carried the canoe out to sea, where it capsized in a storm and Horii drowned. His South Seas Detachment, ravaged by hunger and disease, ended the campaign in the beachheads at Buna and Gona, where from November 1942 to January 1943 the Australians and Americans fought one of the bloodiest battles of the Pacific War. Ioribaiwa and Imita Ridge entered Australia’s memory of 1942 as the places where the Japanese tide halted within sight of Port Moresby.