Cover art
Flint, Eric, and David Drake. In the Heart of Darkness. Baen 1998.

Flint, Eric, and David Drake. Belisarius
Divergence: c 500 CE
What if: An evil empire called Malwa arose in 6th century northwest India and, with gunpowder and in alliance with the White Huns, went on to conquer India.
Series note: Six-volume series including An Oblique Approach, In the Heart of Darkness, Destiny's Shield, Fortune's Stroke, The Tide of Victory, and The Dance of Time. Flint's short story "Islands" is also set in this timeline. The first two volumes were combined in the omnibus volume Belisarius I: Thunder at Dawn and the next two as Belisarius II: Storm at Noontide.
Comments: The first book has cover credit as by Drake and Flint, but all subsequent books were as by Flint and Drake.

Drake, David, and Eric Flint. An Oblique Approach
Divergence: c 500 CE
Summary: A mysterious artifact from the future offers Roman general Belisarius a vision of the Malwa conquest of Constantinople, and he embarks on a dangerous mission into the heart of India.
Series note: First book in Flint and Drake's Belisarius.
Published: Baen 1998 (0671878654w88 android). Included in Belisarius I: Thunder at Dawn, Baen 2008 (1416555684BUY).
Web link: Baen Free Library

Flint, Eric, and David Drake. In the Heart of Darkness
Divergence: c 500 CE
Summary: Belisarius connives and fights his way out of India, only to return to a Constantinople on the verge of overthrowing Justinian.
Series note: Second book in Flint and Drake's Belisarius.
Published: Baen 1998 (0671878859BUY). Included in Belisarius I: Thunder at Dawn, Baen 2008 (1416555684BUY).
Web link: Baen Free Library

Flint, Eric, and David Drake. Destiny's Shield
Divergence: c 500 CE
Summary: Constantinople makes peace with perhaps its oldest enemy, and Belisarius takes the war against against the Malwa to the walls of Babylon.
Series note: Third book in Flint and Drake's Belisarius.
Published: Baen 1999 (0671578170BUY), 2000 (0671578723BUY). Included in Belisarius II: Storm at Noontide, Baen 2009 (1416591486BUY, 1416591664BUY).

Flint, Eric, and David Drake. Fortune's Stroke
Divergence: c 500 CE
Series note: Fourth book in Flint and Drake's Belisarius.
Published: Baen 2000 (0671578715BUY), 2001 (0671319981w88 androidBUY). Included in Belisarius II: Storm at Noontide, Baen 2009 (1416591486BUY, 1416591664BUY).

Flint, Eric, and David Drake. The Tide of Victory
Divergence: c 500 CE
Series note: Fifth book in Flint and Drake's Belisarius.
Published: Baen 2001 (0671319965BUY), 2002 (0743435656BUY).

Flint, Eric, and David Drake. The Dance of Time
Divergence: c 500 CE
Series note: Sixth, and presumably final, book in Flint and Drake's Belisarius.
Published: Baen 2006 (1416509313BUY), 2007 (1416521372BUY).

Flint, Eric. "Islands"
Summary: Novella set in Flint and Drake's Belisarius series timeline.
Published: In The Warmasters (ed. Jim Baen), Baen 2002 (0743435346BUY), 2004 (0743471857BUY).

Flint, Eric, and David Drake. Belisarius I: Thunder at Dawn
Series note: Omnibus volume of the first two books of Flint and Drake's Belisarius.
Published: Baen 2008 (1416555684BUY).

Flint, Eric, and David Drake. Belisarius II: Storm at Noontide
Series note: Omnibus volume of the third and fourth books of Flint and Drake's Belisarius.
Published: Baen 2008 (1416591486BUY, 1416591664BUY).