Nokia's Rolling Thunder strategy for reconquering the US smartphone market continues to struggle after only six months. In its bleak earnings report today, Nokia revealed it shipped just 600,000 handsets in North America during its latest Q2 2012, down from 1.5 million in the same period last year. The 60 percent drop year-on-year, coupled with an identical ship rate in Q1 2012, shows that the company's risky bet on Windows Phone is still a slow starter.

Nokia's 600,000 figure encapsulates phones in general, rather than the specific smartphone segment, but it does show that analyst estimations of 330,000 Lumia sales in the US over a period of around four months may be accurate. The firm revealed four million Lumia sales in Q2 2012, double the previous quarter — but with the lack of phone sales growth and break down of individual device sales it's hard to say whether the Lumia 900 has had much impact in boosting Windows Phone's market share in the US. One thing that is clear from today's results is that, try as it might, the majority of Lumia sales are still outside the US — an important market that Nokia needs to succeed in.