Hello everyone,

Currently, I'm planning on making a strategy game like Superpower 2 (http://www.superpower2.co.uk/screenshots.html)

I only can't completely figure out what kind of library I would have to use, as the game has both 2D and 3D elements. (Can be seen on the screenshots and movie clips provided on the page from the given link).

Can I reach this effect using SFML only, or should I use Directx alongside SFML, or only Directx?

Thanks

All your questions are answered in the FAQ. Never forget to read it.
http://www.sfml-dev.org/faq.php#grl-3d

Every 3D game has 2D elements. I only dabbled shortly with SFML but I am pretty sure it supplies something to create a HUD/GUI with (since I suppose that is what you mean with the 2D part?) Further, A game like that can be made with pretty much any framework/engine that supports 3D.