On the main menu select Skirmish
Change your Home town/Civilization to Russians (St. Petersburg) (The flag Icon next to your gamertag)
Select Deck Builder -> Beginner
Select IV: Industrial Age
Select the 9 Cavalry Archers card to place it in your deck.
Click Save and then back
Change starting age to Post-Imperial Age
Start the game and enter the cheat code: Nova & Orion
Select the flag icon in the bottom right corner of the screen (next to the mini map)
Choose the Beginner Deck
On line IV Select the 9 Cavalary Archers option
This will deliver 9 Cavalry archers to your Town center and will pop the achievement.
Enter cheat code speed always wins to speed this up a bit.
Note: This has to be done using the 9 Cavalry Archers card.