If the Nephilim manage to break through, millions if not billions of Terran lives alone could be lost. While the crew and brave pilots of the Midway tries to cripple and/or destroy the Alien wormhole/gateway, the hastily assembled group of Confed and Border Worlder ships - a Combined Fleet - have to take on the massive Nephilim attack fleet largely within the confines of the Border Worlds space itself. They are outnumbered and outgunned, but they know failure is not an option.
They have to hold off the Aliens long enough for Confed and the Union to reinforce them. They are the ones who have to hold the line.