The army of the ancient Kingdom of Urartu

The illustrations by Alan Buttery may not be ethnic Uratians, but, Iranians from the western Zagros mountains.
The Iranian Warrior, 8th Century BC, in Armies of the Ancient Near East 3,000 BC to 539 BC by Nigel Stillman & Nigel Tallis is based on sculptures of Sargon II at Dur-Sharrukin (Khorsabad; 'Sargon's city'), room 14, 'The Assyrians Besiege and Assault the city of Pazashi (Panzish), in 715BC'
Manna is on the map - south of Lake Urmia within the maximum extent of the Urartian kingdom, so Mannai warriors could appear in a Uratian army as auxiliaries or allies. Zikirtu is just east of Manna.
A similar source is sculptures of Sargon II at Dur-Sharrukin (Khorsabad; 'Sargon's city'), room 2, 'The Assyrians capture Ganguhtu, Bit Bagaya, and Kiundau, and accept the surrender of Tikrakka', in 716BC

One man (upper right) has a shield with chevron pattern. The theory of its construction may be influenced by a Sassanid leather and reed shield, from Dura-Europos, at Yale University Art Gallery. Other Western Zagros Iranians have shields with brick or cross-hash pattern. The shield grip is shown.

Most of the defenders wear the skin-cloak on the right side. An arm hole, as suggested by Stillman & Tallis, rather than a short sleeve may be more likely. An Iranian warrior in room 2 has a skin-cloak over his left shoulder (perhaps with an arm-hole) even though he has a shield. Some Iranian prisoners have skin-cloaks with short sleeve on the left.

Only a minority of Iranians wear laced boots or patterned hems.

Druzhina
Illustrations of Costume & Soldiers