The Algolis Invasion was a Covenant attack on the human colony world of Algolis in the Algol system sometime between 2548 and 2552. The primary target of the invasion was a weapons research facility that was developing advanced weapons systems. While the Covenant were eventually successful in destroying the facility, the UNSC were able to fend off the Covenant assault and secure a strategic victory.
The Algolis Invasion is also known for the infiltration of the UNSC The Heart of Midlothian, which was an attempt by the Covenant to circumvent the Cole Protocol and learn the location of Earth. The plan was thwarted at the last minute by ODST Michael Baird and The Heart of the Midlothian was destroyed before the Covenant could recover any valuable data.