Here’s an an analysis of several leading wargame rulesets for Ancient and Medieval wargaming, ranked from least complex to most complex.

Ancient and Medieval Wargaming (AMW) by Neil Thomas
https://boardgamegeek.com/boardgame/32404/ancient-medieval-wargaming
2 hours playtime; Weight: 1.00 / 5
Buy at: https://www.amazon.com/Ancient-Medieval-Wargaming-Neil-Thomas/dp/0750945729

Resources:
Ancient and Medieval Wargaming
http://theminiaturespage.com/rules/boards/msg.mv?id=1117
http://prufrockian-gleanings.blogspot.com/2013/01/ancient-and-medieval-wargaming-amw-with.html
http://timsbattles.blogspot.com/2012/08/first-play-test-of-neil-thomas-medieval.html

One Hour Wargames by Neil Thomas
https://boardgamegeek.com/boardgame/170298/one-hour-wargames
1-2 hours playtime; Weight: 1.50 / 5
Buy at: https://www.amazon.com/One-hour-Wargames-Practical-Tabletop-Battles/dp/1473822904

Resources:
http://theminiaturespage.com/boards/msg.mv?id=351079

https://boardgamegeek.com/thread/1308184/quick-review-one-hour-wargame

Sword & Spear
https://boardgamegeek.com/boardgame/161726/sword-spear-wargames-rules-ancient-and-medieval-ba
2 hours playtime; Weight: 2.50 / 5

L’Art de la Guerre
https://boardgamegeek.com/boardgame/51429/lart-de-la-guerre
2 hour playtime; Weight: 3.00 / 5

Resources:
http://www.madaxeman.com/L_Art_de_la_Guerre_page.php
http://www.northstarfigures.com/list.php?man=179&cat=140&page=1
http://www.northstarfigures.com/prod.php?prod=6555

Field of Glory
https://boardgamegeek.com/boardgame/31542/field-glory
3 hours playtime; Weight: 3.74 / 5

Discussion on Rules-Light Wargames:
http://theminiaturespage.com/boards/msg.mv?id=210533