Qurani invasion

One thing that seems to definatly be in Dragon age 2 is a qunari invasion of Kirkwall. Which i dont get. The qunari are at war with Tervintar and seem to be struggling to keep it up. it seems reckless to me that they would feel they are ready to divid their forces and launch a navel assult on Kirkwall. It is a logical choice i bet, since it gives them a foothold on the south and gives them an important trade area. But it would also bring them to the attention of Orlais, Nevarra, the rest of the free march nations and Fereldan. Do they really think they have the manpower to hold Kirkwall? Obviously they didnt, since apparently one person (Hawke) was enough to thawt their invasion.