_Diplomacy_ is played with armies and fleets on a single board. Each set of orders results in the state of the board changing. Suppose that, instead of moving the pieces on the board, a second board were set up according to the resolution of the orders given to the first board. If this continued, the whole evolution of the game board could be observed from start to finish. One could even go back to a board state in the middle of the game and give a different set of orders, creating a new version of history and playing out a different game.
Now suppose that, in addition to moving to another province on the board, units could move to _another board_, changing the outcome of the turn and creating a new sequence of boards as the new history plays itself out. This is _5D Diplomacy with Multiversal Time Travel_. Units may move or support into the past, changing history and creating alternate timelines, or move or support into those alternate timelines.
## DATC compliance
When the adjudicator is in a more complete state, this section will declare the extent of the adjudicator's DATC compliance. If no unit attempts multiversal time travel, the game plays out exactly as _Diplomacy_ does normally.
The MDATC (Multiversal Diplomacy Adjudicator Test Cases) document defines test cases that involve multiversal time travel.
## Variant rules
### Multiversal time travel and timeline forks
Just as units in _Diplomacy_ may only move to adjacent spaces, units in _5D Diplomacy with Multiversal Time Travel_ may only move to adjacent times. For the purposes of attacking, supporting, or convoying, turns within one season of each other adjacent. Branching timelines and the timelines they branched off of are adjacent, as well as timelines that branched off of the same turn in the same timeline. A unit cannot move to the province it is currently in, but it can move to the same province in another turn or another timeline.
When a unit changes the outcome of a battle in the past, only the timeline of the battle forks. If an army from one timeline dislodges an army in the past of a second timeline that was supporting a move in a third timeline, an alternate future is created where the army in the second timeline is dislodged. The third timeline does not fork, since the support was given in the original timeline. Similarly, if a unit moves into another timeline and causes a previously-successful move from a third timeline to become a bounce, the destination timeline forks because the outcome of the move changed, but the newly-bounced unit's origin timeline does not fork because the move succeeded in the original timeline.
### Sustaining timelines and time centers
Since there are many ways to create new timelines, the game would rapidly expand beyond all comprehension if this were not counterbalanced in some way. This happens during the _sustain phase_, which occurs after the fall movement and retreat phases and before the winter build/disband phase.
The seven capital supply centers are also considered _time centers_. During the sustain phase, each time center chooses a timeline to sustain. Each timeline with at least one time center sustaining it remains in play. All other timelines dissolve into the ether and cease to be playable. A time center's "vote" is split equally among all timelines and each fraction is owned by the owner of that time center in that timeline.
> [!WARNING]
> The sustain phase is a speculative feature and has not been implemented yet.
### Victory conditions
The Great Powers of Europe can only wage multiversal wars because they are lead by extradimensional beings masquerading as human politicians. When a country is eliminated in one timeline, its extradimensional leader is executed, killing them in all timelines.
> [!WARNING]
> Victory conditions have not been implemented yet.
### Open convoys
The standard _Diplomacy_ rules require that a convoy order include the convoyed unit's origin and destination. This is hard to coordinate once there are multiple turns and timelines involved. _5D Diplomacy with Multiversal Time Travel_ thus introduces the concept of an _open convoy_, a nonspecific convoy order that can become part of a convoy later. An open convoy order does not require specifying the origin or destination of the convoyed unit; the unit is simply told to expect guests. Consequently, it is possible for a unit doing an open convoy to be used by a hostile power to convoy in the opposite direction.
> [!WARNING]
> Open convoys are a speculative feature and have not been implemented yet.
Outside of convoys, a unit may only move one province at a time. Multiversal time travel also allows units to move back or forward by one turn and/or across by one timeline. Since time moves forward by one turn per turn, this makes it difficult to go further back into the past. The _jump assist_ order provides a way for units to intervene deeper into the past. A unit may be ordered to give a jump assist to another unit's move. For each successful jump assist given, a unit may move one more turn or timeline. Jump assists do not grant units the ability to move further geographically than they could otherwise, nor do they provide additional support to an attack.
> Jump assists are a speculative feature and have not been implemented yet.
## Unit designations
In _Diplomacy_, orders refer to provinces, such as "A Mun-Tyr". In _5D Diplomacy with Multiversal Time Travel_, this is insufficient to unambiguously identify a province, since the province exists in multiple timelines across multiple turns. The convention for identifying a multiversal location is `timeline-province@turn`, where `timeline` is the timeline's identifier and `turn` is the turn's identifier, e.g. "b-Mun@3".
(Why this order? Short representations for timelines and turns can be confused for each other, especially for timelines designated with `f` or `s` that might be confused for fall or spring turns. _5D Diplomacy with Multiversal Time Travel_ is already complicated enough, so the timeline and turn are put on either side of the province and delimited with different symbols.)
