Grammatical case in “Brief an Ministerpräsident”

Question

From the Frankfurter Allgemeine:

Elitesoldaten verweigern Einsätze gegen Palästinenser

"Wir wollen kein Werkzeug sein" / Brief an Ministerpräsident Benjamin Netanjahu

Why is it that they use "Brief an Ministerpräsident", even though Ministerpräsident is an N-noun and being used here in the accusative case? (At least, Präsident is an N-noun, or is Ministerpräsident not?)

Answer 1

According to Duden (Richtiges und gutes Deutsch, 6. Aufl. Mannheim 2007):

In case an academic or occupational title is used without a pronoun or article then only the name will be inflected.

Answer 2

You are right: In normal German the phrase should be Brief an Ministerpräsidenten. However, in newspaper headlines you often find that -en-endings are omitted to avoid any confusion with plural forms.
So Brief an Ministerpräsidenten could be (mis)understood as letter to prime ministers. This interpretation can be avoided by writing Brief an Ministerpräsident.

^{One could argue, however, that the plural interpretation should not be possible if Netanjahu is explicitly named.}

Answer 3

In my opinion there is a subtle difference between

"Ein Brief an (den) Ministerpräsidenten Netanjahu"

and

"Ein Brief an Ministerpräsident Natanjahu"

The first emphasizes that the letter is for the prime minister (which happens to have the name Netanjahu) while the second emphasizes that the letter is for Netanjahu (which happens to be prime minister). Just like the difference between "A letter to the President Obama" and "A letter to President Obama".