|“||Time waits for no man.||”|
Siegfried is known as a close associate of the late Albert Einstein. Though Einstein believed his technology should primarily be used for peaceful purposes, Siegfried has set out into the field to show that it is essential to weaponize Einstein's technology in order to protect the free world.
On the battlefield, Siegfried is the man that pilots the "Zeitgeist", a massive craft that wields some of the Alliance's most advanced chrono-technology. He can bombard enemies from a great distance with a cutting edge weapon that creates a small, unstable chrono vortex, inflicting a huge amount of damage to anyone caught up in it. When ordered to deploy, Siegfried creates a large, stable chrono-field, that temporarily phases himself and all friendly units in the area, out of this plane of existence, becoming completely impervious to most outside influence. However, phasing out makes any movement impossible. Due to the bulkiness and weight of his craft, Siegfried can't fit into most smaller transports and cannot cross water. Despite that, he can still make use of Allied air transports.
|“||Commander, if we are outnumbered, I can stall some more units around me, with the chrono bubble. But make sure you send more reinforcements quickly!||”|
|—Siegfried discusses his chrono freeze ability in Zero Signal|
Siegfried is an effective siege hero capable of dealing long range bombardment to his enemies. His weapon fires a powerful, unstable chrono vortex that deals area damage and is highly effective against densely-packed enemy groups or structures.
Furthermore, Siegfried can deploy to create a chrono-field. This field makes himself and surrounding allies temporarily invulnerable to any type of damage, however unable to act and move.
However, Siegfried moves fairly slow due to the bulkiness of his weapon. He cannot be loaded into an Archon AMC and cannot operate its weapon from inside transports. Despite its floating Zeitgeist craft, Siegfried cannot travel across water. Besides that, Siegfried's weapon has a slow firing rate and is unable to fire at any air units. While he is immune to Attack Dogs and Spooks, Terror Drones are particularly threatening to his survival (especially if he is not escorted) as they are fast enough to evade his Zeitgeist Cannon easily.
|“||Commander, the founder of SteinsTech, Siegfried, has arrived to assist you. He is equipped with an experimental long range chrono vortex weapon.||”|
|—Allied intel during Operation: Zero Signal|
|“||There's no way we can let these Russians have the Professor's secrets!||”|
|—Siegfried during Operation: Panic Cycle|
- In Zero Signal, Siegfried is introduced alongside the rest of the Euro Alliance to retake the Radar Domes and neutralise the Soviet Tactical Nuke Silo. He can be defeated without compromising the mission.
- At the start of Panic Cycle, Siegfried accompanies the Battle Tortoise carrying KI Scientists and the MCV and leads a small task force to escort them to the SteinsTech Laboratory. If he falls down throughout the mission, he will reappear next to the SteinsTech Laboratory, but will no longer be controlled by the player. He is one of the very few survivors when the MIDAS hits.
- Siegfried, utilizing his personal chrono backpack suit (see Gallery) instead of the Zeitgeist craft, rescues Tanya from Soviet captivity in The Mermaid. He starts at elite rank and has to survive throughout the mission.
- At the beginning of Puppet Master, Siegfried is chronoshifted into a mind-controlled Allied base and clears the Epsilon presence, giving a chance for an Engineer to capture the Psychic Beacon, reverting the Allied base under their control. He can be defeated without compromising the mission.
- In Stormbringer, Siegfried and Norio help protect a Weather Control Device and later help clearing the Virgin Islands of PsiCorps presence. Defeat of both heroes will not compromise mission failure.
- At the beginning of Insomnia, Siegfried and his initial group will clear the beachhead with the aid of the Paradox Engine's Time Freeze. He's the first of the three Allied heroes to arrive. If he is defeated, he'll be transported to the Paradox Engine to recover, then respawn after a few minutes.
- At the beginning of Unthinkable, Siegfried is among the Allied vanguard sent to destroy the Epsilon HQ base lying between the Allies and their target. If he is defeated, he will reappear through chronoshift against the Epsilon forces after treatment minutes later.
- In Hamartia, Siegfried and Tanya are asked to destroy the last Mental Dynamo protecting the Mental Omega Device in a fortified Epsilon tunnel, then help escorting the Paradox Engine to destinated area. If he falls throughout the mission, he'll be transported to the Paradox Engine to recover, then respawn after treatment minutes later. He is eventually killed by Rahn after chronoshifting the Professor's legacy to an American base in Alaska.
- In Convergence, the player can command Siegfried to destroy the Tech Artillery Bunkers and Coal Plants aside the Panama Canal. Before evacuating, Siegfried must stay alive and act alone on the left bank of the canal. If he is trapped by Magnetron, the mission will fail.
- In the first phase of Parasomnia, Siegfried does not use the "Zeitgeist" device but used his own upgraded chrono backpack to disable the Dybbuk Hives with Tanya and a task force, and cooperate with the European Alliance regiment to destroy the local Epsilon base after all Hives are disabled. During the mission, only one of the heroes is allowed to fall down at most and to be sent back to the Paradox Engine for treatment. When the first phase ends, the two will return to the Paradox Engine.
- In Rainmaker, Siegfried is present among the enemy Euro Alliance forces. He's meant to be avoided by the player (who only has PsiCorps Troopers, light infantry and vehicles) and will leave battlefield along the road later.
- In Blut Royale, Siegfried accompanies Tanya and several brave Allied forces to defend the SteinsTech Academy from the invading Russian and Chinese forces. Defeat of both heroes will not compromise mission failure.
- In Backbitten, Siegfried is one of the guards around the Supercharged Paradox Battery.
- Siegfried's design is visually based off the unused Red Alert 2 concept art for the .
- Siegfried is possibly named after a legendary hero of Germanic mythology, who killed a dragon and was later murdered.
- Siegfried's campaign variant reuses the Cryo Commando sprite.