This is part three of the Belisarius alternate history series. I finished my rereading already, but not my reporting!
The theme is that two sentient devices – or beings – arrive from the future. One, Link, is trying to enshrine racial purity and caste systems and has been giving technology to allow India’s Malwa empire to conquer the world. In the way is the Rome of the 530’s AD, where ability counts more than birth and race. A second device – Aide – was sent to Rome’s greatest general, Belisarius, to fight back.
Although the Nika revolt was crushed, Emperor Justinian was blinded. Unable to hold power, his wife Theodora adopts Belisarius’ stepson, Photius and makes him emperor, with Theodora as regent. Justinian retires to follow his interest in Law, and mechanical development. With the secret out, Rome can openly develop its countermeasures.
But time is short. Already Malwa has launched a two-pronged invasion of Persia. The most dangerous one is the one in Mesopotamia, where the two rivers give a direct route on to Rome itself. The main Persian army has fled into the ruined city of Babylon and is under siege.
Meanwhile in India, the revolt spreads as the Empress Shakuntala takes a port city with her refugees and links up with Rao in Maharashtra.
But Rome has troubles of their own. A revolt in Alexandria ruins plans to make it a base to make gunpowder weapons for the army and for the Axumite and Indian allies. Belisarius has to leave some forces for his wife, Antonia to take to break the revolt and get this into motion again. The rest can go to Persia, but it is a pitiful force against the huge Malwa army.
After a few quick victories, Belisarius is left with a problem. Half of his Persian allies are plotting to avoid the fight to bring down the Persian Emperor. He needs to break the siege of Babylon, but the armies are too large to fight and the supply line on the Euphrates is as sure as sure can be.
Unless Belisarius does something to the river….