Yes, its Evochron Mercenary!

As for aiming, by default the game will auto-aim for you. You can turn this "combat system" off with a single key press though and manually aim for a red marker indicating where the target is going to be when your shot gets there. I'm nowhere near good enough to do that however.

It's pretty awesome, watch a video, grab a demo.
http://www.starwraith.com/evochronmercenary/index.htm

Here goes. This is a prefect example of why I like low budget games.

Earth Defense Force: Insect Armageddon? I doubt it...

EDIT:
Monster Attack?

Earth Defense Force 2017

I'm fine with coming close. I've been running short on ideas about what games to post anyway.

This isn't like VVVVV where I should have known.

I am a bit short myself, but OK

This one should be easy,:

Well that seems to be the Winter War from 1939-1940.

As for the game, my best guess is Hearts of Iron 2.

I thought Hearts of Iron too but the screenies, while similar, didn't seem to quite match up, still if that last guys says no 2 I'll say
Hearts of Iron 3
Why not?

It is neither.

Look at the design of the plan, and the date (upper left). We are in 1918, not 1939 :)

I found something called 'Guns of August' which looks vaugly similar - is that it?

Good try., but nope.

Do you think I should give one more hint ? (or screenshoot ?)

This video should at least help you identify the era :

http://www.youtube.com/watch?v=tntA_4IoxbE&feature=player_detailpage

http://www.youtube.com/watch?v=tntA_4IoxbE&feature=player_detailpage

[The video are not part of the game]

So that would make it the Finnish Civil War. Hmmm...

Oh... not only