The main attack was planned for 1 April, but as the various Japanese units moved into position, a number of minor probes were made by elements of the Japanese 6th Engineer Regiment in the Australian rear areas and along their line of communications.
The first raid came on the night of 27/28 March, when a force of about 100 Japanese exploited a gap between the 25th Infantry Battalion's main defensive position and its 'B' Echelon—which included its transport and logistics elements and was protected by a company from the 61st Infantry Battalion—fixed bayonets and then assaulted the rear of the Australian perimeter.
The Australians had been alerted to their approach after the communication line between the two positions had been cut, and when the attack began the men had already been roused and the weapons pits fully manned.
As a result, the attack failed and was turned back.
A number of Japanese survivors managed to dig-in near the perimeter and later fired upon the Australian clearing patrol that was sent out the following morning, as well as snipe at the company defending 'B' Echelon's position.
Afterwards, the Australians counted 19 dead Japanese around their position, while they also managed to capture one of the wounded.
Against this, the 25th Infantry Battalion had lost three killed and seven wounded.

Another probe was made early on the morning of 28 March on the positions of the Australian 5th Field Battery, whose eight guns were located east of Toko, on the west bank of the Puriata River from where they could provide defensive fires in support of the 25th Infantry Battalion's main positions on the knoll.
Shortly before dawn one of the booby traps that the Australians had set around their perimeter to provide early warning was set off and one of the sentries opened fire upon what he believed to be a Japanese probe.
A short time later, a small section of Japanese stumbled into one of the forward positions and fire was exchanged.
Later, as a team was sent out to disarm the remaining booby traps, this team was fired upon and sporadic fighting continued until midday.

That evening, around 23:00, the 9th Infantry Battalion's rear echelon at Barara, along the Toko–Mosigetta–Buin Road, came under attack.
Under the command of the battalion second-in-command, and possessing only four Bren light machine guns for direct fire support, they were nevertheless able to hold off the initial attack.
Following this, sporadic fighting continued into the early morning, when at 04:45 on 29 March a force of about 100 Japanese attacked the position supported by sustained machine gun and rifle fire.
Rushing the Australian position with bayonets, they were beaten back by stiff defence and fell back from the position, leaving behind 23 dead but taking their wounded with them.
Four Australians were wounded in this encounter.

Throughout 29 March, the Japanese continued the tactic of using small-scale attacks to test the Australian defences and isolate the 25th Infantry Battalion's forward companies from its headquarters and rear.
Over the course of the morning and into the afternoon, one of its companies was probed, while the headquarters also came under attack.
The company from the 61st Infantry Battalion protecting the 25th Infantry Battalion's line of communications also came under attack from the 70 Japanese that were believed to be entrenched between the 'B' Echelon and the 25th's main positions, suffering two killed and two wounded.
Later, it became clear to the Australians that the Japanese were preparing for a major attack against Slater's Knoll, following the capture of a Japanese sergeant who confirmed that the probes were, in the words of Gavin Long, the "prelude to a full-scale offensive".

These probes intensified on 30 March, as one of the 25th Infantry Battalion's companies was strongly attacked by the Japanese.
The Australian position had been weakened by having about a third of its strength out on patrol at the time of the attack.
Unable to return to the perimeter while the company was under fire, they were forced to link up with
The main attack was planned for 1 April, but as the various Japanese units moved into position, a number of minor probes were made by elements of the Japanese 6th Engineer Regiment in the Australian rear areas and along their line of communications. The first raid came on the night of 27/28 March, when a force of about 100 Japanese exploited a gap between the 25th Infantry Battalion's main defensive position and its 'B' Echelon—which included its transport and logistics elements and was protected by a company from the 61st Infantry Battalion—fixed bayonets and then assaulted the rear of the Australian perimeter. The Australians had been alerted to their approach after the communication line between the two positions had been cut, and when the attack began the men had already been roused and the weapons pits fully manned. As a result, the attack failed and was turned back. A number of Japanese survivors managed to dig-in near the perimeter and later fired upon the Australian clearing patrol that was sent out the following morning, as well as snipe at the company defending 'B' Echelon's position. Afterwards, the Australians counted 19 dead Japanese around their position, while they also managed to capture one of the wounded. Against this, the 25th Infantry Battalion had lost three killed and seven wounded.
Another probe was made early on the morning of 28 March on the positions of the Australian 5th Field Battery, whose eight guns were located east of Toko, on the west bank of the Puriata River from where they could provide defensive fires in support of the 25th Infantry Battalion's main positions on the knoll. Shortly before dawn one of the booby traps that the Australians had set around their perimeter to provide early warning was set off and one of the sentries opened fire upon what he believed to be a Japanese probe. A short time later, a small section of Japanese stumbled into one of the forward positions and fire was exchanged. Later, as a team was sent out to disarm the remaining booby traps, this team was fired upon and sporadic fighting continued until midday.
That evening, around 23:00, the 9th Infantry Battalion's rear echelon at Barara, along the Toko–Mosigetta–Buin Road, came under attack. Under the command of the battalion second-in-command, and possessing only four Bren light machine guns for direct fire support, they were nevertheless able to hold off the initial attack. Following this, sporadic fighting continued into the early morning, when at 04:45 on 29 March a force of about 100 Japanese attacked the position supported by sustained machine gun and rifle fire. Rushing the Australian position with bayonets, they were beaten back by stiff defence and fell back from the position, leaving behind 23 dead but taking their wounded with them. Four Australians were wounded in this encounter.
Throughout 29 March, the Japanese continued the tactic of using small-scale attacks to test the Australian defences and isolate the 25th Infantry Battalion's forward companies from its headquarters and rear. Over the course of the morning and into the afternoon, one of its companies was probed, while the headquarters also came under attack. The company from the 61st Infantry Battalion protecting the 25th Infantry Battalion's line of communications also came under attack from the 70 Japanese that were believed to be entrenched between the 'B' Echelon and the 25th's main positions, suffering two killed and two wounded. Later, it became clear to the Australians that the Japanese were preparing for a major attack against Slater's Knoll, following the capture of a Japanese sergeant who confirmed that the probes were, in the words of Gavin Long, the "prelude to a full-scale offensive".
These probes intensified on 30 March, as one of the 25th Infantry Battalion's companies was strongly attacked by the Japanese. The Australian position had been weakened by having about a third of its strength out on patrol at the time of the attack. Unable to return to the perimeter while the company was under fire, they were forced to link up with 
Battle of Slater's Knoll