The Valkyrie is a variable fighter originally designed along the lines of technology retrieved from a crashed alien spaceship known as the SDF-1. The machine possessed three different modes allowing a human pilot to not only fight in the air, but on the ground as well in a mecha form. The Valkyrie appeared in Super Dimension Fortress Macross, and the american adaption that became known as Robotech.
Due to the split in continuity, the Valkyrie has two different albeit similar versions detailing its history: the Macross version and the Robotech Version.
In Macross, after the SDF-1 crash landed on earth humans inspect the wreckage, and discover that it was a war vessel manned by giant aliens. This lead to a global war to unify the nations under a world government, and during this war against nations who wished to remain independent, the U.N. Spacy began development on what would be come the VF-1 Valkyrie. The first was the VF-X which was just a jet fighter used to test designs for what would become the VF-0, the prototype to the VF-1 Valkyrie, that was only capable of flight within the atmostphere. In the year 2009 of the Macross timeline the VF-1 saw it's debut combat on Arteria Island against giant alien invaders known as the Zentradi. The VF-1 had the capability of fighting in the vacuum of space, and in it's mecha form, known as Battroid mode, could fight in close quarters. The VF-1 Valkyrie was the main fighter used during Space War I, but it was only deployed for a few years before being replaced by an upgraded design.
In the Robotech continuity, the history surrounding the Valkyrie was almost the same except for the order of events it was created and the names surrounding the modes of the fighter and locations where the Valkyrie saw battle. Also the Robotech version of the Valkyrie did not go through as extensive test stages as its Macross counterpart.
In future installments of Macross and Robotech, the VF designs would be expanded upon creating new models that were more advanced with each installment.
The VF-1 Valkyrie came in a multitude of different designs such as the VF-1S, VF-1J, and VF-1A. The main difference in these models were the heads of it's mecha form, and what armaments and loadouts it was capable of using. The Valkyrie was designed to have three modes: Fighter, GERWALK, and Battroid (Fighter, Guardian, and Battloid modes in Robotech)
The Fighter mode was simply that of a jet aircraft fighter that was similar in design to F-14 Tomcat formally used by the United States in real life. In this form the VF-1 could be outfitted with a wide range of misses and laser turrets. In some depictions it could be outfitted with a type of armor that would remain attached to it as it transformed.
In GERWALK mode (Guardian Mode in Robotech) which stood for "Ground Effective Reinforcement of Winged Armament with Locomotive Knee-joint" was a sort of half transformation between the fighter form and the mecha form. in this mode the fighter would transform giving the fighter arms and legs while retaining some of the mobility of a fighter.
In Battroid mode (Battloid mode in Robotech) the VF-1 Valkyrie would fully transform into it's mecha state. The laser turret would then be used as a type of rifle for combat against the giant alien forces of the Zentradi.