Byzantine Armenia in the context of "Mamikonian"

Western Armenia (Western Armenian: Արեւմտեան Հայաստան, Arevmdian Hayasdan) is a term to refer to the western parts of the Armenian highlands located within Turkey (formerly the Ottoman Empire) that comprise the historical homeland of the Armenians. Western Armenia, also referred to as Byzantine Armenia, emerged following the division of Greater Armenia between the Byzantine Empire (Western Armenia) and Sassanid Persia (Eastern Armenia) in AD 387.

The area was contested during the Ottoman–Persian Wars and was conquered by the Ottoman Empire during the wars of 1532–1555 and 1623–1639. The area then became known also as "Turkish Armenia" or "Ottoman Armenia", and included six vilayets. During the 19th century, the Russian Empire conquered sections of Western Armenia, including Kars.

The Muslim conquest of Armenia occurred in the mid-7th century, with the first Arab raids into the country occurring in 639/640. At that time, the Byzantine and Sasanian parts of Armenia had just been united under the Byzantine-aligned Armenian prince Theodore Rshtuni. Several Arab attacks and Byzantine-Armenian counterattacks occurred in the 640s. In 652, facing a renewed Arab assault, Rshtuni broke with the Byzantines and made an agreement with Mu'awiya, who was then governor of Syria, and accepted Muslim rule. Rshtuni's death in 654 and Arab internal conflicts after 656 temporarily weakened Arab control over Armenia, but Arab rule was decisively reasserted after Mu'awiya's accession as caliph in 661.

Sasanian Armenia, also known as Persian Armenia and Persarmenia (Armenian: Պարսկահայաստան – Parskahayastan), may either refer to the periods in which Armenia (Middle Persian: 𐭠𐭫𐭬𐭭𐭩 – Armin) was under the suzerainty of the Sasanian Empire or specifically to the parts of Armenia under its control such as after the partition of 387 when parts of western Armenia were incorporated into the Eastern Roman Empire while the rest of Armenia came under Sasanian suzerainty but maintained its existing kingdom until 428.

In 428, Armenian nobles petitioned Bahram V to depose Artaxias IV (r. 422); Bahram V (r. 420–438) abolished the Kingdom of Armenia and appointed Veh Mihr Shapur as marzban (governor of a frontier province, "margrave") of the country, which marked the start of a new era known as the Marzpanate period (Armenian: Մարզպանական Հայաստան – Marzpanakan Hayastan), a period when marzbans, nominated by the Sasanian emperor, governed eastern Armenia, as opposed to the western Byzantine Armenia which was ruled by several princes, and later governors, under Byzantine suzerainty. The Marzpanate period ended with the Arab conquest of Armenia in the 7th century, when the Principality of Armenia was established. An estimated 3,000,000 Armenians were under the influence of the Sasanian marzpans during this period.