I need your help picking a series title!

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I need your help picking a title for a new series!
I am currently working on a brand new military science fiction series probably set to release mid-summer of this year, but I’d like your opinion on a prospective title!
The series is going to take place in the near future, when a privately financed spacecraft is making the first commercial orbit of the Moon. During the flight, an alien spaceship comes out of hyperspace and takes the lunar mission ship aboard. The aliens are known as the Helta and they tell the humans that there’s a war going on and the Helta are losing. They have no experience in combat and despite more advanced technology, they’ve lost world after world to the ruthless Tevynians. They need our help to save their Alliance, and they’re willing to give us advanced technology, including starships, in exchange.
The United States, Britain, Australia, Poland and a few others take up the challenge, and the very first human troops on the front line are the First Extraplanetary Expedition Force, led by a Ranger company in powered armor…who are promptly nicknamed the “Space Rangers.”

Which would get your interest more as a series title for these books?

Earth At War
United Stars
Earth Force

 

Please contact me atdutyhonorplanet487@gmail.com to let me know your choice!