Nath : First off, our commanding officer, during our military service, was an earth pony, and no magic or air tricks could save us from getting our butts kicked … even after we got promoted Captains.
He personaly trained Goliath, to help him leash his strength.

Now, I’m not from Equestria, but as soon as I’ve learn to read pony, I’ve consult history volumes telling about the Dark Age, the “Before Equestria”, when ponies couldn’t get along, and increasing conflicts led to the loss of Ponylands.
Earth ponies knew that they would be the easiest target for the two other factions, so they quickly adapt and use their ingenuity and creativity to  build devices that would give them more than a chance to fight on equal terms with pegasus and unicorns alike.
From highly trained warriors to master engineers machinery and anti-magic specialists (Unicorn Hunters), earth ponies never backed down.
We apparently owe them some devices that we still use nowadays.

Finaly, even if it’s not an exemple that I would like to share, one of the main threats for the kingdom today comes from no one else than an Earth pony … WildCard …