The player’s task card.
 The player’s geographical situation.
 The economic system of the game.
 The game calendar.

Two main types of army.
The pros and cons of mercenaries.
Fortresses, armies and geography. 
A third type of army? 
Commanders. 

Strictly speaking, "Interregnum" is the full game which can be played by three to five players, whereas "Konradin", which appears as "1264 Konradin" is a two-player variant scenario. This scenario uses the standard rules for the most part, but with such additions and deletions as are necessary for its own peculiar situation. The following description of the game therefore concentrates on "Interregnum".

Each player represents one major faction in the Germany of the period, and in the course of the game players can raise armies, fight field battles, storm fortresses and conduct sieges. Family members of a faction can enter the Church to become members of the clerical nobility (one abbacy, a large number of bishoprics and six archbishoprics are available) or marry neutral nobles (or family members of other factions) with the aim of gaining "permanent allies" and thereby pick up extra contingents of knights. A faction can intervene in feuds which are being carried on between neutrals (clerical nobility, lay nobility and towns) with the object of gaining "temporary allies" which can provide a range of different troops with different capabilities. A faction’s armies can conduct hunts. Success in certain actions gives a faction access to a wide range of other advantages, drawn from one of the card decks which is known as the "Concealed Opportunities" deck.

At the beginning of the game, each faction receives a task card. The first faction to fulfil the conditions of its task card wins immediately. There are five such task cards and they all differ from one another, so that each player’s card is unique. One such card demands that the player’s faction has to elect and crown one of its family members as sole king. Another demands that the faction has to amass a huge fortune in cash. Yet another demands that the faction has to raise a large force of knights and/or mercenaries, while another states that the faction must raise a smaller, but still substantial force of knights. The final card requires the faction to hold a tournament attended by a number of nobles. A very large number of optional rules add considerable colour and variation to a game which is already a colourful and varied opus magnum. Such optional rules provide for ambuscades, assassinations, bribery, winter quarters, trading with the Hanseatic League, increased rates of movement and improvements in the military leadership qualities of one’s family members, to name but a few.

Little wonder therefore that the author of the game, in his introduction to the German language rules, describes it as "very complex". Potential players however, should not be put off by this comment, as it is only true up to a point. Admittedly, the rules are long and there are many of them, but they are thoroughly presented, and the core rules are straightforward and very logical. In practice, the game should present few, if indeed any, problems for a reasonably experienced board gamer.
The game is played over a maximum of six game years, each of which is divided into twelve months, with each month representing one game turn. The game year can also be thought of as representing three "seasons", i.e., 1) a true campaigning season from April to August, during which one’s troops will serve with only the initial, very large payment which they receive in April, 2) an extended campaigning season from September to November when one’s troops will serve with a repeat of the April payment each month, and 3) a winter season from December to March, during which no military activity can take place. At the end of the November turn, all armies which are on the board have to be disbanded. Disbanding an army at any time during the year costs as much as it did to raise it in April,although payments are not made to disband an army in any month during the game year or to pay troops in the extended campaigning season, provided that the army in question has had a military success in the same month. (Presumably the troops satisfy their greed for gold by looting - but this is, quite obviously, a very important rule.)

Play is conducted on a beautifully produced map board representing mediaeval Germany and parts of surrounding countries. The map board is divided into areas by a combination of rivers, differing types of terrain and special types of border fortresses which are termed "blocking fortresses". The alpine areas have special movement rules. Most areas contain at least one, and more usually several fortresses which range from a castle with a rating of "1" and an intrinsic garrison of 100 to a city with a rating of "5" and an intrinsic garrison of 2,500. The fortresses which represent a faction’s initial feudal holdings are depicted in that faction’s colour. All other fortresses are neutrals and are uncoloured.

Since each faction can raise up to three armies, each turn consists of up to three phases. Each army I is phased in player order for the turn, followed by each army II in player order followed by each army III, again in player order.

Essentially, an army’s phase consists of either movement into a neighbouring area or redeployment between friendly armies which occupy the same area. A player may choose not to move or re-deploy. Secondly, the army is permitted to carry out an action. Such an action may be non-military (marriage, election of a king, a coronation or a hunting expedition are examples of this), or it may be military (attacking an army in a field battle, storming a fortress or laying/continuing a siege are typical examples). Rivers cannot normally be crossed unless the faction controlling the army in question holds a fortress in the same area which has a bridge across the river. Such fortresses need not necessarily be part of the faction’s initial feudal holdings - the fortress may belong to an ally or it may have been captured earlier in the game and retained. Failing this, one has to seek permission to cross at a fortress which one does not control. If the fortress controlling the bridge belongs to another faction, verbal confirmation of permission to cross will suffice, of course, but if the fortress belongs to a neutral noble or town, one tests for permission by rolling a D4. This can be modified by offering payments in cash.

Field battles are straightforward as are storm attacks upon fortresses, but in order to make such attacks, certain numerical criteria have to be met (80%+ of the opponent for a field battle and 300%+ of the strength of the fortress in a storm attack). The same is true for sieges. To lay a siege requires 150%+ of the strength of the fortress, but a siege goes on to last for a number of turns which are equal to the rating of the fortress. At this point, the fortress becomes demoralised, and its strength falls to 50%, thus allowing the siege to be ended by storm attack (i.e., the attacker will now have 300%+). In the case of a neutral fortress, it is also possible to demand its surrender in each turn in which the siege continues. One tests for compliance by rolling a D4. Naturally, in calculating the strength of a fortress, one has to add the strength points of any faction troops which it might contain to its intrinsic strength.
With every field battle or storming of a fortress, it is necessary to check the intensity of the battle (1xD4). The result of this will provide a modifier for the survival dice roll (2xD6) which has to be made for each and every male family member (attacker’s and defender’s) who has taken part in the conflict. One can certainly lose family members and "permanent" allies (such as sons-in-law) in such circumstances. Since each army must be led by at least one such male family member or by a son-in-law, loss of such individuals can prove very troublesome. The actual resolution of a field battle or a storm attack is done by rolling 2xD6 against the appropriate table, which takes the relative strength of the attacker against the defender into consideration. There is one table for field battles and another for storm attacks.

In a siege against a fortress with a river bridge, the fortress has to be invested from both sides of the river, with the main force (which by itself has to match or exceed the numerical criteria required) on the fortress side of the river. A similar rule applies to sieges against "blocking fortresses". Some fortresses are therefore less vulnerable to siege than others.

Only army counters are moved on the map board, and the only other counters which may be deployed thereon are markers which show the locations of allied, captured, destroyed or currently besieged fortresses, plus another set of special markers which show the current locations of marriages and where feuds are in progress. The remaining counters, such as family member counters (5 male and 5 female per player) together with associated cards belonging to the factions are deployed off-board with each player arranging his own into army groups and/or a reserve. An army organisation sheet, which must be photocopied for each player, is provided to facilitate this. There are also several card decks, including those of the neutral nobility and the towns, concealed opportunities etc., which must be laid out in the areas provided for them at the edge of the board.

The opportunities to train family members for the clergy or to obtain marriages for one’s family members with a view to gaining "permanent" allies (so gaining more knights) or to engage in feuds which occur amongst neutral nobles and/or towns (so gaining more knights or mercenaries) represent an important aspect of the game, not least because several of the task cards ultimately depend on the player obtaining such allies. Cards are drawn from the appropriate card decks along the edge of the board and are laid in special boxes offering 1 clerical post, 2 marriages (one male and one female) and three feuds (two cards per feud - and a player can intervene on either side). The ensuing locations of the marriage and feud opportunities are also marked with special markers on the board. The appropriate card is replaced as and when such a situation is either resolved or when it is changed by the "change of offers" die-roll which occurs at the beginning of most game months. This last is done by a roll of a D6, and any player may demand a re-roll by paying a sum of money. Indeed, several such re-rolls may occur in any one month as various players may object to the range of results as not being in their interests.

There are, in fact, three methods of winning the game. The first, which is in accordance with the players’ task cards has already been mentioned above, and this method is valid for the entire length of the game. In game years 5 and 6, any two players may ally and attempt to obtain a joint victory by fulfilling a completely different set of conditions. If this too fails or is not attempted and if the game reaches the end of year 6 without a victory, the winner is determined by totting up victory points. In practice, the game is almost always won by the first method.

This game is certainly challenging. Players will find that they have a great deal to think about in terms of their own individual victory conditions and how to attain them. A player is advised to try and work out what his opponents’ task cards are and how close they are to fulfilling their victory conditions as the game progresses. A player will have to compare his own position to those of his opponents’ - or at least what he perceives to be his opponents’ positions - and act accordingly. Circumstances can be quite fluid, and a player will have to be flexible in his strategies and tactics.

With repeated play, one finds that one learns more about the more subtle strategies and tactics of the game. Careful play can lead one’s opponents to misjudge one’s position, often to their subsequent chagrin. What appears to be a brilliant strategy may turn sour. One particular faction, the Brabanters, whose base is in north-west Germany and Flanders never receive the task card requiring the sole elected and crowned king (for historical and game mechanism reasons). Accordingly, other players are likely to persuade this faction to elect and crown one of its family members - or one of two foreign princes - as German king because this will cause problems for the player who does have the task card requiring him to do this. They may well provide him with monetary, military and material help to accomplish this. This strategy appears ideal - but what if the game finishes at the end of year 6 with the totting up of victory points? A king is worth a lot of victory points… . It is for reasons of this sort that I feel that it is in the application of the rules rather than in the rules themselves that players will find their greatest challenges (in the best sense of the word), and this is particularly true as the game, when played well, is very interactive.

The game has a simple and effective economic system, which is very "tight" and therefore capable of causing problems for the unwary player.

The rules have been translated into English. A possible problem is that, at the time of writing, there are actually only very few sets left available of the current second edition.