What’s the point of triumvirate, as political regime?

Question

Triumvirate is a very frequent pattern of government, and almost every area or the world, in almost every age, shows examples of it.

I’m Italian, and thus I am particularly familiar with the notion, because it recurs many times, both in Ancient Rome history, and in the Risorgimento (Italian national unification) eve, and even in some early stage of Fascismo, if I am not wrong.
(Well, I’m wrong: it was the Quadrumvirate. Nobody’s perfect.)

That fact is quite surprising, provided that notoriously triumvirates seldom are effective, while usually just one member out of the three is the real leading person.

So, why did the triumvirate occur (and keeps on happening) so often in political history?

Answer 1

There are several reasons for this:

1. There are usually, naturally, several centers/poles of power. Ordinarily, they would compete.

   In a single-ruler scenario, these centers of power - especially when evenly matched - would have to fight each other (in most points in history, by pure force).

   Combining them into Triumvirate, preserves their power - both in terms of their combined strength being overwhelming, and more importantly, because they do not waste that strength fighting each other.

2. Sometimes, a Triumvirate would comprise of people with different expertise/strengths. Someone is skilled at strategy, someone at political persuasion, someone at finance. As usual with a collective, the sum total may be bigger/better than the parts.

3. 3 is a magic powerful number.

   OK, Potter, go sit in the back of the class, we know you failed History of Magic.

   No, seriously, 3 is kind of a magical number:

   • It's odd. That means that there is no possibility of logjam by having equal number of votes on each side of an issue. This rules out 2 and 4 member systems.

   • It's not too big, this still being autocratic power system instead of a committee. That would rule out 5+ member systems; where some of the members would invariably be weaker.

Answer 2

I think that more than "political system" it is a consequence of group dynamics.

• Too few: If you have a duumvirate, you have two personalities in direct conflict and no counterbalancing system:

  • Either one of them is the "senior" member and the other is the "junior", and both accept the situation: but in this case we will often not consider that a duumvirate but the senior member being the ruler and the junior member a supporter.

  • They do not accept a hierarchy between them; the two members see themselves as equal in power. That often leads to conflict (conspiracies, civil wars, ...) making the duumvirate an unstable solution, as any of the members may believe at any time that they are capable of removing the other one.

    The only stable variation would need well defined spheres of influence of each member (e.g. a civil leader and a religious leader), and even those situation lead to conflict.

• Too many: with 4 or more, the ruling group can split themselves into groups/factions, with each group selecting its own leader (you could consider Julius Caesar Civil War a case of that). That devolves into a duumviare or triumvirate.

In opposition, in a triumvirate, in the case of conflict between two members the third one can act as arbiter; even if any of the two members in conflict does not agree with the final resolution to the conflict, he may find himself too weak to challenge the other two members of the triumvirate put together.

That is not to say that a triumvirate is any kind of a magic solution; while certainly better than duumvirates they are rather scarce. With time, any two members of the triumvirate may ally themselves and conspire to remove the other one, leading to a duumvirate or even single ruler.

In most of these apparitions of triumvirates, I think it is worth looking closely at the particular circumstances that led to them (what did each member of the triumvirate apport to the group) than to try to establish a general rule. The notable exception could be Fascist Italy, that due to its "hobby" of trying to mimic the Roman Empire could have done so just as an imitation of the famous (and failed) Roman triumvirates.

Answer 3

• Having an odd number of people means there will be a clear majority unless one of them abstains. In a well-balanced triumvirate, any two members can check the third and stop ill-conceived notions.
  This applies if they hold formal votes and also if they are simply three roughly equal warlords.
• The same decision process would also work for one, five, seven, and so on, but with five members three of them could form a much slimmer majority. Note the use of seven or nine for panels of judges.