After being freed and restored in the army Martirosyan became a division chief of staff, beginning World War II in that capacity.

During the Russian Civil War, in March 1918, Martirosyan joined the 19th Workers' Battalion of the Red Guards, with which he took part in the defense of Baku from advancing Ottoman forces in the Battles of Kurdamir, Goychay, and Shemakha.

After the Ottoman capture of the Transcaucasus and the overthrow of the Baku Commune in September, Martirosyan crossed through Georgia to Armenia and was unemployed.

In June 1939 he was freed due to lack of evidence, restored in the army and appointed chief of the operations section of the staff of the 121st Rifle Division of the Belorussian Special Military District.

Martirosyan was transferred to the Kharkov Military District in March 1941, where he served as chief of staff of the new 227th Rifle Division at Slavyansk.

With the arrival of re-appointed division commander Colonel Yefim Makarchuk Martirosyan returned to his primary duties as chief of staff.

Makarchuk characterized Martirosyan as a "tactically competent chief of staff...quickly orienting himself in the situation, skillfully organizes the direction of the troops and implementation of command decisions.

The recommendation read:[4]Comrade Martirosyan has served as commander of the 340th Rifle Division during the battles against the German-Fascist occupiers near Tula.

In the most tense moment of the battle for the village of Rudnevo, Comrade Martirosyan personally led the attack of the 1144th Rifle Regiment, inspring the soldiers and commanders to a rapid advance forward.

After receiving replacements, the division returned to the 38th Army on 23 April, and took up defenses southwest of Sudzha on the line from the Psel to Krinichnoye.

Martirosyan was transferred to command the 73rd Rifle Corps of the 2nd Ukrainian Front's 52nd Army in April 1944, leading the 73rd for the rest of the war.

For exemplary fulfillment of objectives and displaying courage and heroism Martirosyan was recommended for the Order of the Patriotic War, 1st class by army commander Konstantin Koroteyev on 15 May.

Commanding the 73rd Rifle Corps from June 1943, he led his formation through the fields of Ukraine, and in difficult battles defended every inch of native Ukrainian soil.

In the destruction of the Korsun-Shevchenkovsky grouping, in the destruction of thirty enemy divisions in the Jassy-Kishinev operation, in the breakthrough of the powerful, deeply echeloned enemy defenses in the vicinity of Yassy, Romania, the 73rd Rifle Corps under the command of Major General Martirosyan always was on the main axis and always successfully carried out the tasks of the army military council.

On 12 January 1945, the 73rd Rifle Corps inflicted a destructive strike against the enemy forces on the Sandomierz bridgehead and pursuing the shattered units rapidly moved forward.

In the course of all combat operations during the Great Patriotic War Major General Martirosyan displayed exemplary mastery of the knowledge of commanding troops, courage and valor in battle, and selfless loyalty to the Motherland.