19:30 Jan 29, 2011 

I have learned - thank you, Michel. Votre explication m'a convaincu, d'autant plus qu'il s'agit d'un "secteur d'activité".

16:25 Jan 29, 2011 

In spite of capital letters, "Génie combat" désigne une spécialité (et non pas un corps, ou une branche) - par opposition à "génie infrastructure" (ou "génie infra"), which is "infrastructure engineers" (http://www.infrastructureengineers.com/).
D'ailleurs, cela convient mieux dans le contexte d'une lettre de motivation!
Therefore, IMHO, "corps of engineers" or "combat engineer" do not exactly match the query.

14:10 Jan 29, 2011 

My understanding is that "Génie militaire" is military engineering as a sector of engineering and that "Génie combat" is the military corps that does it. I agree that there is an important question about whether the "Génie combat" is purely concerned with combat intervention or whether they also are involved with more general infrastructural support. My first reference seemed to me to imply the latter.

13:46 Jan 28, 2011 

...denote a proper noun. In this case, the name of a branch or component: Combat Engineers. (Incidentally, such a branch does not exist in the (UK) Corps of Royal Engineers.)

13:24 Jan 28, 2011 

...on the style you choose for "Génie militaire."