When are relative pronouns preferred to possessive pronouns and how common is this?

Question

Question prompted by this sentence from Wikipedia:

Nach einem Überfall am 13. Mai 2014 auf einen Stoßtrupp der 7. Infanteriedivision in der Region Chibok wurde beim anschließenden Truppenbesuch des kommandierenden Generals dessen Fahrzeug von eigenen Soldaten beschossen.

I found the following from a Google search:

According to A. E. Hammer "German Grammar and Usage" 165v: A particular use of the genitive is to replace the possessive adjective when the latter might be ambiguous.

I understand that "sein" can be used here instead of "dessen" and that "dessen" is less ambiguous but which is more common and are there any instances where a possessive pronoun could be used instead of a relative pronoun but really shouldn't be/would sound very odd?

Answer 1

As you already pointed out in your question, replacing dessen with sein in the original sentence would create an ambiguity. The sentence could still be "parsed" and understood, because applying sein to any of its other then possible targets (Überfall, Stoßtrupp, Truppenbesuch) makes no sense. This general is introduced and mentioned for the first time within this sentence. sein could be more appropriate, if the general had been established as the acting subject, like this:

Nach einem Überfall am 13. Mai 2014 auf einen Stoßtrupp der 7. Infanteriedivision in der Region Chibok [stattete der kommandierende General seiner Truppe einen Besuch ab. Dabei wurde sein] Fahrzeug von eigenen Soldaten beschossen.

Concerning "... used instead of a relative pronoun ...": The dessen here is what I would call a "grammatical false friend", it looks like a relative pronoun, but is in fact a demonstrative determiner (of so called deictic form), qualifying the vehicle as the general's (genitive).

For the sake of completeness, relative would mean to rephrase as something like

Der General, dessen Fahrzeug beschossen wurde ...

There is no way to substitute a reflexive here, except maybe for (incorrect) slang uses

Eigene Soldaten beschossen dem General-sein-Fahrzeug, ...

^{(for the perfectionists: This last example can be grammatically correct in a different context, but that would be off topic here).}