The Divided League

Planets
Hermes is a human colony planet.
Babur is a subjovian planet.
Mirkheim is a source of industrially valuable supermetals.

Organizations
The Polesotechnic League comprises the Home Companies, the Seven in Space and the independents.
The Supermetals Company is non-League.

Secrets
The Seven have armed Babur.
The Supermetals Company, helped by an independent, has not artificially generated the supermetals that it sells but mined them on Mirkheim.

Now that the second secret is out:

Babur claims Mirkheim;
the Home Companies say that the Solar Commonwealth should control Mirkheim;
the leading independents argues that Mirkheim, a stateless planet, should be protected by the League, which Supermetals would join;
Supermetals asks Hermes to take possession of Mirkheim;
the Seven say that the League should deal with whichever power gains Mirkheim.

How many sf novels present a four-sided conflict?

Van Rijn, the leading independent, meets Lennart of the Home Companies and Story of the Seven. They cannot agree but some things are learned from the meeting. Story knows that van Rijn helped Supermetals. Lennart lets slip that the Commonwealth has sent a task force to Mirkheim...

In Mirkheim, as in The People Of The Wind, Poul Anderson shows various groups of people gradually moving towards and preparing for war on an interstellar scale. Let us hope that this never happens in reality.

There is also humor. Van Rijn's waist is described as "...his Jovian equator." (Rise Of The Terran Empire, p. 66) His churchwarden pipe "...had seen years of service and grown fouler for each day of them." (p. 67) If only life could remain on that level.

See also here and here.