The Dead Hand system, officially known as War Protocol Neptune's Vengeance (Eurasian: Ultio Neptunis), is a Eurasian nuclear warfare military protocol to be followed by nuclear submarines in the Eurasian Fleets. It is written by the Emperor of Eurasia, who often takes many weeks to fully finish the messages, which are thought to be identical copies of each other but may be customized for each submarine. These are typed personally by the Emperor and are also signed by him. The orders are for what actions the submarines should take, given that Julium and the Empire have been destroyed in a decapitating strike. Eurasia maintains many failsafes to ensure there is always one individual to take the Imperial throne and rule the Empire. However, the Dead Hand system was developed to be the naval parallel to Pluto's Wrath, both of which are designed to ensure that any decapitating strike against Eurasia will be met with a greater measure of destruction.
Each letter is sealed in a secure compartment of the submarine and is only to be opened in the event of total nuclear war. It is assumed that even during a nuclear war, the Julian Palace will continue issuing orders, as it is extremely unlikely that the Emperor or all his heirs designate will be killed. Thus, the submarines are not expected to ever be required to utilize the letters. However, the option exists.
The letters are thought to contain several options for commanders to follow. These include: "place yourself under the command of Duresia, if it exists," "place yourself under the command of the highest ranked surviving military official," "retaliate with full force," and "use your own judgment." Given declared Eurasian nuclear policy, any option which does not include full retaliation is highly unlikely. No copy of the letters has ever been released, and they are burned unopened after the death of the Emperor.