@Klaue: You and enemy both get XP when you kill AND when you lose soldiers. So it's not strange he advances through the ages even though you build no soldiers for him to kill. I believe designer did this on purpose, otherwise game would be VERY easy (it's quite easy as it is).
Also, sixspeed made a good point. I normally watch the whole turn sequence: maybe AI put some reinforcements in the region or transfered troops from adjacent areas. If you skip to the end, you don't get to see all this stuff.
@KazzarEkly: I see. Although my comment still relates to your situation (you really had tough break losing with those odds, but I that's not a usual norm)... Unlike normal Risk, WarLight has only 1 round per battle - so unless you destroy all enemy units, the rest of your invading force will return to the point of origin (you can say that they've been beaten back by defender).
@barbarth: You need to play Airlift card and then select "120" reinforcement stack as though you're selecting a map region. Proceed to select transfer region and... presto! Although, you'll get only 119 units, because game considers reinforcement stack as a separate region (so you need to leave at least 1 unit on it). Moreover, you can transfer this reinforcements to your ally also (otherwise, enemy AI will eat him alive before the end of turn 8 or so).
The battle system is not frustrating. It's unlikely to lose when you have 3:1 army ratio (it happens sometimes); with 4:1 or more, it's practically impossible. The challenges are possible, but only if you play very aggressively - you need to expand constantly, in multiple directions.
Second try on harder: gave up on 44th day. Lost 11 men, including the only leader and scientist. Got attacked 10 times or so, plus 2 hordes (with 3rd approaching). ._.
Got 4 fever kills in 4 days while at the same time being attacked by 2 zombie hordes in 3 days. Lost 6 survivors (7 in total), all before 35 days passed. Harder mode is indeed for masochists...
So... anyone has advice for level 26? Both robots are nigh-unkillable (even with headshots) and they kill you with a single grenade (for example, I stuck one with 4 and it only removed half of his health).
 "Age of War"){kind=icon}
 "WarLight"){kind=icon}
 "Rebuild"){kind=icon}
 "Raze"){kind=icon}
 "Man in Gap"){kind=icon}