They would find us, realize we have some minerals and resources that are common on our world, but rare on theirs, and ask for a trade agreement while introducing themselves. No peace, no war, just introduction and mutual agreements. It could lead either way at that point. Eventually they would trade technology, and relationships could either decrease or increase, and with luck we'd have two sentient species living on one world.
Would also lead to some political chaos as to what to do about this (which is highly likely to finally cause global unity).
Would also lead to some political chaos as to what to do about this (which is highly likely to finally cause global unity).