From Valve:
Steam's Wargames Fest brings a full week of discounts and demos on all kinds of wargames on Steam and runs on April 28th through May 5th at 10am Pacific on Steam.
What types of games does that include? Any kind that has you leading teams to battle, whether fictional or historic. Find yourself commanding troops in the middle of a world war; fight on multiple fronts in the Napoleonic era; or lead fellow players through battles on space warships and Steampunk airships!