The Allied council demanded that Romania leave Tiszántúl and respect the new borders. Romania said it would only do so after the Hungarian Army demobilized. Kun said he would continue to depend on the might of his army. On 11 July, the Allied council ordered Marshal Ferdinand Foch to prepare a coordinated attack against Hungary using Serb, French and Romanian forces. Hungary, in turn, prepared for action along the Tisza River.
On 20 July, in the northern arena, the Hungarians army took Rakamaz and some nearby villages. Troops of the Romanian 16th and 2nd Vânători divisions took back the villages shortly and regained Rakamaz the next day. The Hungarians renewed their efforts and, supported by artillery fire, retook Rakamaz and two nearby villages but could not break out of the Rakamaz bridgehead.
On 20 July, Hungarian forces established a solid bridgehead on the east bank of the Tisza at Szolnok, opposed by the Romanian 91st Regiment of the 18th Infantry Division. The Hungarian army moved the 6th and 7th divisions across the Tisza River, formed up within the bridgehead, then attacked the Romanians in the first line of defense. The Hungarian 6th Infantry Division took Törökszentmiklós; the 7th Division advanced towards Mezőtúr and the 5th Division advanced towards Túrkeve.
On 21–22 July, Hódmezővásárhely changed hands several times between Hungarian and Romanian troops of the 90th Infantry Regiment supported by the 1st Vânători Brigade. On 23 July, Romanian forces reoccupied Hódmezővásárhely, Szentes and Mindszent.
On 24 July, the Romanian 20th Infantry Division, brought in as reinforcements, cleared the bridgehead at Tiszafüred. Not being able to break out of Rakamaz, Hungarian forces fortified their positions and redeployed some troops. There was a lull in fighting in the north, as the Romanian troops did the same.
On 24 July, the Romanian Army's northern maneuver group attacked. Elements of the 2nd Cavalry Division, supported by troops of the 18th Infantry Division, took Kunhegyes. The Romanian 1st Infantry Division attacked the Hungarian 6th Infantry Division and took Fegyvernek. The Romanian 6th Ddivision was less successful, being counterattacked on the left flank by the Hungarian reserve formations. Altogether, the attack pushed back the Hungarian army 20 kilometres (12 mi). Romanian forces were supported by the 2nd Vânători Division and some cavalry units when they became available.
On 25 July, fighting continued. Hungarian forces counterattacked at Fegyvernek, engaging the Romanian 1st Infantry Division. With their lines breaking, Hungarian troops began a retreat towards the Tisza River bridge at Szolnok.
After repelling the Hungarian attack, the Romanian army prepared to cross the Tisza River. From 27–29 July, the Romanian Army tested the strength of the Hungarian defense with small attacks. A plan was made to cross the Tisza River near Fegyvernek, where it makes a turn.
On the night of 29–30 July, the Romanian Army crossed the Tisza River. Decoy operations were mounted at other points along the river, bringing intense artillery duels. Romanian forces held the element of surprise.