The battles to gain possesion of the Ourcq River and the ground near it began on 27 July and ended on August 2, 1918. On 27 July, the Rainbow soldiers were ordered to prepare for an attack across the Ourcq River.

An abbreviated description by J.J. Cooke, however, mentions some movements of the 150th Machine Gun Battalion:

The two brigades would advance in columns of regiments moving seiftly to the river, force a crossing, and seize the high ground directily north of the river. The action was to begin with a heavy artillery bombardment...Facing the river, the 83rd Brigade would assault with the 165th New York leading the way, backed up by the 166th Ohio and the 15th Machine Gun Battalion [emphasis added; this was Joe's unit]...

German artillery hit the assault regiments. [The 42nd advanced and was forced to fall back.] The Ourcq would not be crossed on 27 July. The 12th aero squadron was now attached to the division, with the task of aerial observation...another try at getting troops across the Ourcq on the 28th...to push the enemy hard. By 9 a.m. , both the Iowans and Alabamians had crossed the river to take the small town of Sergy...

The New York 165th had also assaulted across the Ourcq before dawn; their objective was the stone complex of Meurcy Farm, less than a mile from the river. Casualties mounted...On the morning of 29 July, the Germans counterattacked Sergy and drove the Rainbows back to the river. The enemy had complete possession of the air.

It became necessary to go after [German] machine gun positions one by one with small groups, one group firing to keep the gunners down while the other group of Americans rapidly bounded to another position. Once in place, they in turn began firing, occupying the German machine gunners while the other group moved. The Rainbows had moved forward only about two kilometers at best. By 4 pm, the Ohio 166th was able to assault Seringes-et-Nesles and attack the eastern slopes of Hill 184 in conjunction with the French. By the end of 29 July, the Rainbows had finally taken the towns and heights that overlooked the Ourcq River...a new set of obstacles...barbed wire barriers.

Air observers [On 30 July] and 165th scouts reported that the Germans were placing more wire and obstacles near the Chateau de Nesles, and this information was forwarded to Colonel McCoy's PC.38 In the afternoon, the 165th reported to Reilly that it was taking flanking fire on its left from German machine gunners. Could McCoy's Illinois gunners silence those positions? They did, and the Irish inched forward. By 8:45 P.M. Reilly was certain that McCoy's men had taken their basic objectives. He ordered his gunners to replenish their ammunition to prepare for the next day's fight, which promised to be a harder one.

Disease was becoming a problem. The water supply was often polluted...Corpses floated in the Ourcq River...Rations had to take second place to ammunition and medical supplies...supplymen were attacked...men in the front lines simply went hungry and thirsty as flow of supplies dwindled.

By the evening of 31 July, the Ohio 166th were in firm control of the town of Seirnges-et-Nesles...vicious fighting...hand-to-hand, clubbed rifle, and bayonet...High ground north of the Ourcq River was finally in Allied hands...bought at a terrible price.

By 2 August, the Germans were pulling back to the Vesle River in good order...artillery barrage continued. The Allied advance was a slow one...The Rainbow Division was used up, tired, and incapable of any sustained operation such as a puruit. The 4th Division relieved the 42nd Rainbows on the night of 3 August.