For the next 24 hours, you can earn Strikes by defeating bases in the Incursion mode.
Bronze and Silver crates have a small chance to drop a Strike and Gold crates are guaranteed to contain at least one Strike. You’ll even have the chance to win Strikes that are currently beyond your player level. Strikes will only drop from PvP battles (not War Zones) and by using Scout mode (not Revenges).
Here are the stats for each Strike: https://warcommander.com/2017/04/10/strikes-have-arrived/
Give ‘em hell, Commander!