Earlier today i was playing the campaign mode, and had entered turn 31. By this point i had around ten ships (decent builds) and they were guarding two joined (and attackable by enemy) planets.
Upon entering into the 32nd turn, i was attacked on both planets. Each enemy fleet consisted of around 10-18 empire cruisers. In both battles i lost miserably, so miserably in fact that i could never have won even if all my ships were defending.
Although this annoyed me, i was able to see a possible reason for this. When i deployed my fleet for the second battle i already had ships deployed (that i had not built). ships from a previous campaign and of a different design. thinking this was some sort of miracle i deployed my ships, and found that when the fight began the additional ships were not present.
I believe that there is a bug telling the game i have more ships than is possible, and this may be the reason for such un-winnable enemies so early on.