A platoon from B Company, PIB under Lieutenant Arthur Smith departed Port Moresby on 7 June to patrol the Barena–Buna area, with the remainder of the company following on 14 June under the command of Hooper, tasked with patrolling the Ioma, Mambare, Morobe, Waria River, and Garaina areas. A platoon from A Company under Lieutenant John Izatt was already in position at Waria River and was attached to B Company. On 24 June the battalion headquarters under Watson and C Company moved forward from Port Moresby to the Kokoda–Awala area. Meanwhile, B Company, 39th Battalion was sent overland via the Kokoda Track to secure the Buna area and prepare to oppose any Japanese advance, while the PIB was already north of the Owen Stanley Range at the entrance of the Kokoda Track. Maroubra Force arrived at Kokoda on 15 July. Yet despite initial Allied patrols and engineer reconnaissance into the area, the Japanese had ultimately been able to move faster, seizing the initiative. As a result, these small parties would ultimately be the first to make contact with the Imperial Japanese forces upon their landing in Papua. Having already captured much of the northern part of New Guinea in early 1942, the Japanese landed on the north-east coast of Papua, establishing beachheads at Buna, Gona and Sanananda. On the night of 21/22 July, 3,000 Japanese landed near Gona in an attempt to advance south overland through the mountains of the Owen Stanley Range to seize Port Moresby as part of a strategy of isolating Australia from the United States. Initially only limited Australian forces were available to oppose them, and after making rapid progress, the Japanese South Seas Force under Horii clashed with understrength Australian forces at Awala on 23 July, before forcing them back to Kokoda. During the PIB's first engagement Lieutenant John Chalk's platoon had participated in an ambush of the Japanese troops advancing towards Kokoda. Chalk and a scout party had moved to Sangara on the night of 22 July where they observed a Japanese force camped. The next morning he reported their arrival by runner and was ordered by Watson to engage them. That night, Chalk and his 40-man platoon ambushed Japanese forces from a hill overlooking the Gona–Sangara road, killing several before withdrawing into the jungle as they quickly responded with small arms and mortar fire. Meanwhile, elements of B Company, 39th Battalion under Captain Sam Templeton had begun arriving and they moved to cover the Papuan withdrawal.