Keyes Loop
From Halopedia, the Halo wiki
The Keyes Loop was a space tactical maneuver first executed by, then, Commander Jacob Keyes at the Battle of Sigma Octanus IV. The result was one of only three decisive space victories achieved by the UNSC over Covenant forces and it led to Keyes' promotion to Captain.
Summary
Arriving over Sigma Octanus IV in response to a possible impending Covenant attack, the UNSC Iroquois found itself outmatched by the arrival of a Covenant battle group consisting of one carrier, one destroyer, and two frigates (medium-sized ships). This was contrary to the expectation of four medium-sized ships.
Commander Keyes resolved to attack. The Iroquois set a collision course for the destroyer at emergency acceleration while launching a nuclear warhead in what seemed the wrong direction. The two escorting frigates proceeded to launch a salvo of plasma, but the Iroquois managed to evade by utilizing the emergency thruster. Having missed their target, the plasma came about and continued to track and home in on the UNSC warship.
The trailing ordnance was to prove critical to the success of Keyes' strategy. A last minute course correction allowed the Iroquois to merely "graze" (scrape) the destroyer's shields rather than smash directly into the ship properly, resulting in the destruction of a large portion of the Iroquois' armor (Keyes had torn through 2 meters of titanium and had breached every bottom deck of the Iroquois). However, the tracking plasma was unable to correct for the sudden maneuver of their target and, in consequence, impacted on the destroyer instead. A heavy salvo of Archer missiles sent the remaining Covenant warship to its destruction.
With the momentum built up during the first phase, the Iroquois performed a slingshot maneuver around the planet. Once safely away, the nuclear warhead deployed earlier, was detonated, completely draining the shields on the two frigates. Having completed its orbit, the Iroquois resumed its attack and destroyed the two frigates with two heavy MAC rounds and hundreds of Archer missiles left. Its escorts destroyed, the carrier then disengaged and escaped out system but not before leaving 34 dropships and a small ship, the Covenant Destroyer, to continue the ground assault. Later on the Carrier hailed the rest of the attack fleet to Sigma Octanus IV.
