After Vulcan decided to stay out of the war they offered warp detection technology to the rest of the Coalition of Planets and it was installed shortly thereafter. However, the system turned out to be ineffective so Earth forces began installing upgrades in all their systems. Columbia (NX-02) was sent to Altair to install these upgrades.
As the Columbia was installing the upgrades to the early-warning system, they detected the system's outer nodes failing and moved to investigate. They soon picked up a small convoy of 16 Romulan attack ships and engaged them, destroying 14 Romulan fighters immediately. The two remaining fighters sped into the inner system and were engaged by the Daedalus-class ships, USS Heinlein and USS Kon-Tiki, resulting in the destruction of one of the fighters. The final fighter attempted to make a suicide run against the planet, but was destroyed by Columbia just moments before it impacted the surface.
While Altair was saved, it was proven that there were still gaps in the effectiveness of the detection grid and that Starfleet still had to work out the issue. (ENT - The Romulan War novel: Beneath the Raptor's Wing)