[7]: 161–163 During World War I, in 1916–1917, Romania and Russia fought as allies, and during the winter of 1916/1917 the Russian command directed the 35th Infantry and 15th Cavalry divisions to the Romanian front in order to forestall the country's complete occupation.

Gaining the support of the Romanian government, the party agitated for the introduction of Moldovan language in state institutions, solving the agrarian problem only in the interest of Moldavians, and gradually promoted a union with Romania.

[8]: 23  Simultaneously, the internal situation in Russia also led to emergence of Bolshevik groups among the Russian soldiers: distinct organizations were created in Bessarabia and the Romanian Front during August and September.

[22] Despite Romanian military support, Shcherbachev, who according to van Meurs had become a "commander without an army", failed to subdue the local Bolshevik committee and ultimately agreed to sign an armistice with the Germans.

According to Tutula, these troops aimed at suppressing Shcherbachev, dethroning King Ferdinand I and establishing a communist regime in Romania; such arguments determined the Romanian Government to adopt, on the night of 21 December [O.S.

[8]: 27  Determined to combat the Central Powers and Russian forces hostile to its interests, the head of the French military mission in Iași, General Henri Mathias Berthelot, began pressuring Romania to occupy Bessarabia.

[8]: 31 The socialist bloc and the block of national minorities in Sfatul Țării were categorically against the arrival of the Romanian troops, indicating that this could be the first step to the military occupation of the region, posing a threat to all the political and social gains of the revolution.

in preparation for repelling an impending intervention, they created a unified command in Chișinău, the Revolutionary Military Committee for Bessarabia, headed by Yevgeny Venediktov and using both troops from the reserve regiments and units retreating from the Romanian front.

[31] On 6 January, the Romanian government, in agreement with the Ukrainian authorities, ordered Transylvanian troops to advance from Kiev to Chișinău, in coordination with an attack on the border town of Ungheni, which had a Bolshevik garrison.

[20]: 371 [16]: 64–65 [8]: 32  Attempts by Erhan and Inculeț to convince the Moldavian troops to release the Transylvanians, claiming they were only in transit, failed after the captured soldiers declared they had been sent to take over Romanian depots and liquidate the Bolsheviks.

The Romanian troops and Russian detachments led by general Nekrasov, Shcherbachev's representative, retreated toward Ungheni and attempted to regroup at Cornești during 20 January, only to be surrounded by a revolutionary railway battalion.

Some of the invading troops surrender, while the rest managed to break out and retreat to Romania; general Nekrasov barely escaped lynching by his soldiers and was ultimately killed by locals.

[8]: 33 Around the same time, the Romanian army along with Russian troops loyal to Shcherbachev attempted to create a bridgehead in the south of Bessarabia, occupying Cahul, Vadul lui Isac and Manta.

[20]: 373–374 In the meantime, Ion Giurcă claims the Bolsheviks attacked the headquarters of the Inter-Allied Commission, arresting the military and officials of the Entente states, as well as several deputies of Sfatul Țării.

[19]: 511 [20]: 377  According to Vladimir Polivțev, factors that led to failure of the Chișinău defence included the general inferiority of the troops, mismanagement of the existing units, inter-party frictions among the various Soviet organizations and the success of supporters of the Sfatul Țării among the officers to neutralize part of the Moldavian regiments.

Rudiev personally called for guarantees for freedom of speech, assembly, and the inviolability of the members of the congress, demanded the restoration of a sovereign Moldavian Republic, with the Romanians expelled from the country within 24 hours.

[8][20]: 382–384 : 39  As the Defence Headquarters decided to send regular troops across the Dniester for reorganization and replenishment, the Red Guards also bore the brunt of the Romanian attack on the city, which begun on 29 January.[which?]

A wave of brutal reprisal began against the local population, with the Romanians putting around 5,000 residents under armed guard near the railway station, and confiscated food stocks from Bender and the neighbouring villages.

Later that day, a rally was held that was attended by 3,000 workers, soldiers of the garrison and representatives of nearby villages, expressing protest against the entry of the occupation forces into Bessarabia and subsequently weapons from the military depots were distributed to the population.

On 3 February 1918, the 1st Romanian cavalry division crossed the Prut at Sculeni and advanced towards Fălești, where it was fired upon by the Red Guards; the town was ultimately captured after two successive attacks.

Romanian attempts to break into Bălți from the south on 4 February were repulsed by machine gun and artillery fire, and the attacking troops were forced to retreat by the heavy losses.

[20]: 389–391 [8]: 38–39  Several days later, the Bulgarian peasants in Taraclia assembled a 250-strong detachment armed with rifles, scythes and pitchforks, but the town surrendered after the Romanian artillery opened fire.

The following day, Romanian monitors of the 2nd Marine Division shelled the town and the transport ships present in its harbour, prompting the K-15 floating battery to return fire.

While auxiliary ships managed to leave the harbour, the Soviet gunboats succeeded in damaging one Romanian monitor and destroying their artillery fire-directing centre, forcing them to retreat upriver.

On the same day, Field Marshall August von Mackensen, Commander of the German-Austrian troops, met the newly appointed Romanian prime-minister Alexandru Averescu in Iași in order to discuss a peace treaty.

Mackensen personally assured Averescu that Romania would be able to maintain troops in Bessarabia and would receive freedom of action against the Soviet in exchange for signing the peace with the Central Powers and supporting the export of agricultural products from Ukraine.

Thus, according to Ciobanu, in an appeal to the citizens of Chișinău, members of the Bessarabian government denied that the Romanian troops had ever been invited to occupy the republic, stating that their only purpose was to take control of the railways from the Bolsheviks.

[23]: 33  Marcel Mitrasca claims that the benefits brought by the restoration of public order and the assurances of the Romanians that they will not interfere in the Bessarabia's political life determined many people to change their attitude.

[3]: 38 [30] This move was condemned by the Soviet government as a flagrant violation of previous agreements and devoid of legal power, while the Ukrainian People's Republic severed diplomatic relations with Romania and issued financial sanctions against Bessarabia.

[7]: 170–172 Between April and May 1919, when the Bolsheviks had already firmly established their rule over the Ukrainian Black Sea coast, the Red Army developed a plan to reconquer Bessarabia and come to the aid of the Hungarian Soviet Republic.