Oly Oly Oxen Free

Oly Oly Oxen Free is a six-note tone used as an all clear code by the SPARTAN IIs. They had learned it from Deja when they were younger, and had used it ever since they first trained on Reach.

Psychology
Oly Oly Oxen Free was very secret to the Spartans- no one but them and a select few outsiders knew it. These outsiders were close to the Spartan family, such as Dr. Catherine Halsey, Cortana, and Sergeant Johnson. The signal was thus very important to each Spartan, who would rather die than give up the significance of the tone, which could betray or endager their teammates.

Uses
Oly Oly Oxen Free was used on numerous occasions throughout Halo: The Fall of Reach and Halo: First Strike. Some of the times it was used are:


 * After the Spartan Team had beaten Tango Company, and John-117 had checked to make sure their evacuation point was all clear.
 * After The Battle of Reach, Anton-044 used it as an S.O.S. signal over the E-Band.
 * for the Spartans to enter CASTLE Base, Kelly-087 used it to let Dr. Halsey know it was them.
 * During Operation: FIRST STRIKE, Linda-058 used it to let John know where she was so he could pick her up.

Links

 * Spartan Language