How did a vacuum inside an early incandescent bulb protect its carbon filament?

In an early incandescent bulb, the vacuum served a critical protective function for the carbon filament. By removing the air from the glass bulb, the vacuum prevented the filament from oxidizing—a process that would have caused it to burn away almost immediately when heated to incandescence by an electric current.12

Essentially, the absence of oxygen allowed the filament to glow steadily for extended periods without being consumed by combustion. This innovation, made possible by the development of effective vacuum pumps, was a key factor in transforming the incandescent lamp into a practical and reliable source of light.12