- This article is about an in-universe event. For the in-game mission, see Front Line.
- "Don't worry about us, we shall stand firm and fight to the end!"
- ― Colonel Perrault
Operation Vanguard was an Osean defense operation during the Circum-Pacific War. Yuktobania attempted a landing operation to capture Sand Island Air Force Base and begin invading Osean territory, and even went so far as to deploy the Scinfaxi underwater aircraft carrier once more.
The 108th Tactical Fighter Squadron "Wardog" had just returned after defending the SSTO launch to the Arkbird. They returned in time to assist in the defense. The odds didn't favor them. They were the only experienced pilots there. The others were killed on the bombing raid on the island. They were able to bring some cadets from Heierlark Air Force Base, but they never saw action.
- "They shot that from outer space?"
- ― A Yuktobanian soldier after seeing the Arkbird use its laser to destroy a burst missile
The battle started with the Yuktobanian landing forces at the beaches, which was faced with the Sand Island's beach defenses. Wardog and the rookies attacked the ships that bombarding the shore. They sank a few ships before the Scinfaxi attacked. Luckily, the Arkbird appeared and destroyed a burst missile with its laser, allowing the air force to destroy the ships. Soon, the Scinfaxi launched a salvo of missiles at the planes. The Arkbird was able to destroy a few missiles, but was unable to destroy them all. Wardog was able to climb above 5,000 feet, but the rookies couldn't make it and were shot down. The anti-submarine plane Blue Hound detected the submarine and sent data to Arkbird. The Arkbird then fired its laser into the ocean and forced the Scinfaxi to surface. It was attacked by Wardog and then damaged again by the Arkbird's laser. It ripped a huge hole and Blaze shot a missile into the interior and destroyed the Scinfaxi.
The raid on Sand Island was a major turning point. With the destruction of Scinfaxi and most of the landing forces, Yuktobania was unable to replace the losses. Hrimfaxi, Scinfaxi's sister ship, was there in the area too, but escaped without taking a single hit from Osean forces to Razgriz Straits. From now on, Osea would be on the offensive.