The collapse of the Russian Tsarist empire with the Russian Revolution of 1917 gave a chance to the Armenian Revolutionary Federation to create the new republic. The triumph of Bolsheviks in 1917 put an end to the Russian Empire. When it was established borders were with the Democratic Republic of Georgia in the north, the Ottoman Empire to the west, the Persian Empire to the south, and Azerbaijan Democratic Republic to the east. Armenians faced the total annihilation as the 100 thousandth Turkish army crossed the pre-war Russian frontier, annexed the city of Kars and approached the Armenian capital of Yerevan. After having depopulated the Western Armenia, the Turkish military were now about to destroy the rest of Armenia and achieve their goal of eliminating the Armenian nation.

The leaders of Dashnag party, recognizing the problem under the slogan of "The fatherland is in danger" started creating an Armenian army.  The Armenians raised an army of 40,000 men, including soldiers, officers and volunteers.

The Turkish army starts attacking, hoping to finish the Armenian issue once and for all with one last stroke. By May 23rd they take Hamamlou, Gharakilise, Pash Abaran, Sartarabad and Sourmalou on the banks of the river Arax.

On May 21, ignoring the retreat, colonel Daniel Beg Piroumian gets behind the Turkish army in Sartarabad and starts hitting them from the sides. The surprised Turkish army gets disorganized and scared. 

This heroic act encourages the Commander of the Araradian front, General Movses Siligian on May 23rd to order the attack on Sartarabad. People and army, rush the enemy. 

On the Arakats front, General Tro's army counter attacks and after fierce battles Armenians take back Pash Abaran and start advancing towards the fields of Shirag. 

The Armenian soldiers, gathered in Tilichan, go on the offensive on May 26 under the command of General Thomas Nazarbegian on the Gharakilise front, stop the enemy and take control of the war. 

On May 28, Armenian forces are victorious everywhere and the Turkish army is in defeated retreat. Some 30 thousand of Turkish soldiers were killed; the Turks were flung out. Vahib-Pasha, the defeated Turkish commander, termed the Armenian soldiers as "the best fighters in the world". The Armenians also held defenses at Karaklis and at Abaran.

On the same day of May 28, 1918 Armenia was proclaimed an independent republic. The Armenian National Council, under the leadership of Avedis Aharonian, declared the creation of the Democratic Republic of Armenia.

Independence day in the Democratic Republic of Armenia, 1919

The Armenian government and the legislature are transferred from Tbilisi to Yerevan in July 1918. Quoting the Prime Minister "Under Rain, Chaos and catastrophic conditions" the new government starts its work.

The Republic had four Prime Ministers during its existence, all of whom belonged to the Armenian Revolutionary Federation (more). Hovhannes Katchaznouni (30 June 1918 - 28 May 1919), Alexander Khatisyan (28 May 1919 - 5 May 1920), Hamazasp Ohandzhanyan (5 May 1920 - 25 November 1920) and Simeon Nazari Vratsyan (25 November 1920 - 2 December 1920). Aram Manougian (more) was the first minister of Interior. 

During the 1919, the leaders of the Republic had to deal with issues on three fronts: domestic, regional, and international. The Armenian Congress of Eastern Armenians that took control in 1918 fell apart and in June 1919, the first national elections were held. During 1920's, which began under the premiership of Hovannes Kachaznuni, Armenians from the former Russian Empire and United States developed the judicial system. January 1919 was an important milestone as the first University was founded.

The European powers found themselves unable to solve the Armenian Question. The unification of the Caucasian Armenia with the Turkish Armenia proclaimed by the Armenian government in 1919 turned out Utopian. After Armenia was officially recognized by the governments of Allies and by the United States, the US President Woodrow Wilson was invited to determine the borders of the Armenian State. According to Wilson's map, a new Armenia would include most of its historically belonging lands. The project would never come true.
 

In 1920, the Democratic Republic of Armenia administered an area that covered most of present-day Armenia, and Kars, Iğdır, Çıldır and Göle districts of Ardahan, while the regions of Nakhchivan, Nagorno-Karabakh, Zangezur (today the Armenian province of Syunik), and Qazakh were disputed and fought over with Azerbaijan. The Oltu region (shortly administered by Georgia in 1920) was also claimed by the Democratic Republic of Armenia. The majority-Armenian area of Lori was disputed with and administered by Georgia. The Armenian Army managed to control the regions except for Karabakh which came under stable but temporary Armenian control, though Azerbaijan continued to assert its claims over the areas.

The new state faced fatal internal and external problems. Armenia exploded into anarchy as the Armenian Bolsheviks rose in the cities of Nakhichevan, Alexandrople and Kars. The Soviet government hypocritically negotiated with both Dashnak and Bolshevik leaders of Armenia.

First republic of Armenia -Western boarders as it was drawn by than US  President Woodrow Wilson

In August 1920, the Treaty of Sèvres, signed by England, France and Turkey, bound Turkey to recognize the independence of Armenia and the Wilsonian boundaries. The new Armenian state was recognized by most of the countries, including the United States. However, after the triumph of Mustafa Kemal, the Turks, supported by the Bolshevik Russia, attacked the infant Armenian Republic again. The Armenian and Russian Bolsheviks played a fatal role in demoralizing the population and the Armenian army. The Bolshevik propaganda now called the Turks "socialists" and "friends of Russians". On the other hand, the victorious Russian XI Red Army, after successfully Sovietizing Baku, Azerbaijan, and Karabakh, approached Yerevan to "overthrow the Dashnaks". The disoriented Armenian army retreated, surrendering Kars. The whole Armenian population there was then pitilessly butchered by the Turks.

Armenia gave way to communist power in late 1920. The Soviet 11th Red Army invasion started on the 29th of November 1920. The actual transfer of power took place on December 2 in Yerevan. Armenian leadership approved an ultimatum, presented to it by the Soviet plenipotentiary Boris Legran - who was at work as one of major Russian diplomats on Caucasus at that time. Armenia decided to join the Soviet sphere, while the Soviet Russia agreed to protect its remaining territory from the advancing Turkish army. Soviets also pledged to take steps to rebuild the army, protect the Armenians, not to pursue non-communist Armenians, etc.

When on December 4, 1920, the Red Army entered Yerevan, the government of Armenian Republic effectively stopped working. On December 5, the Armenian Revolutionary Committee (Revkom; made up of mostly Armenians from Azerbaijan) also entered the city. Finally, on the following day, December 6, Felix Dzerzhinsky's dreaded secret police, the Cheka, entered Yerevan, thus effectively ending the existence of the Democratic Republic of Armenia. What was left of Armenia was under the control of a communist government. The part occupied by Turkey remained for the most part theirs - by the subsequent Treaty of Kars. Soon, the Armenian Soviet Socialist Republic was proclaimed, under the leadership of Aleksandr Miasnikyan. It was to be included into the newly created Transcaucasian Soviet Federated Socialist Republic.