Fortunately, we've already been prepared for possible cow uprising by The Farside comics. There is something else we need to focus on though...
Gliese 581g InvasionAccording to a very reputable source (the Daily Mail, which I understand is infallible from what our British brethren have to say) some flashes of light were detected coming from Gliese 581g soon after its discovery. I don't know whether these were subspace signatures, RKV launches, some kind of nuclear saber rattling, or the intergalactic equivalent of giving the finger, but it's definitely a threat, and it happened 20 years ago! This means we're
way behind those dirty Gliesians.
So there are two orders of business:
1. Prepare for the invasion (of Earth

)
Really, I just wanted an excuse to quote this post I saw on 4chan (a threat in its own right) on this same topic that I liked. It's regarding the suspected response to our beaming a bunch of twitter messages to the Gliesians (actually, the first stage of our psychological warfare campaign).
don't worry they probably won't be able to decode it even if they get it. At most it'll just let them know that we're here. In 40 years if we get a few more plasma burst we'll know that yes, they are there and they do want to communicate.
either that or in 300 years we'll be invaded, but by that time our gundams will block out the sun and they'll have to fight in the shade, which they'll probably be accustomed too due to their wonky tidal locked orbit.
2. Prepare for the invasion (of Janus

)
Gliese 581g (or Janus as I like to call it, owing to the tidally-locked two-faced thing going on) is far away, and it's going to take us a while to build a fleet to get there and school their extra-terrestrial hineys. Fortunately building spaceships is what we (HLP) do best and MjnMixael recently built a subspace drive, so we've got that covered. Not to mention we have about a kajillion hours logged in space combat simulators.
Ground combat will be another story. Surface gravity there is about 1.3g, so start hitting the gym. Secondly, being tidally locked, we're going to see some extreme weather there. I propose we deploy our Finnish and other high-latitude members to the night side and our more equatorial members to the day side (myself included). We'll fight our ways towards the terminator and meet up in the middle where the weather is sweet, then celebrate our victory with rivers of Bosch Beer.
.....but
until then, watch yourselves! There are still many more threats out there and we can't have any of you going and getting killed before the invasion. Stay vigilant brothers!