Maybe some alien civilization does know about us, but it slightly afraid since we spec’ed in the war tree instead of space travel.
They kept letting us advance our war machines until one day they needed us. To help stop a greater evil; since they went space exploration instead of guns
Building interstellar spacecraft requires advanced automation. Nuclear energy has obvious weapons uses. If there is higher density energy than nuclear, to power spacecraft, then it too can be weaponized.
If they’d need our help, it could only be fighter jets, and they’d need a capacity to hover in the enemy atmosphere, with a space ship large enough to act as an air strip. You can’t drop tanks in the middle of nowhere without fuel and other logistics.