IDC, in its report on Q2 global smartphone shipments, offered a breakdown of Windows Phone devices by manufacturers. The report indicates that Nokia was the primary Windows Phone device manufacturers with 7.1 million devices shipped (81.6% of total). Second place went to Samsung with 1 million unit shipments (11.5% of total), while HTC was in third place after shipping 400,000 units (4.6% of total), and Huawei was fourth with 200,000 unit shipments (2.3% of total).
Given Nokia's focus on Windows Phone, the first result is not a surprise, but what is notable is that Samsung has overtaken HTC for the second spot in the Windows Phone manufacturer league table compared to the same period last year. This can, in part, be explained by the relatively late arrival of the ATIV S in some markets, compared to the HTC 8X (newer devices tend to sell in higher numbers), but it is impressive that Samsung has achieved this shipment number with just a single Windows Phone 8 device (ATIV S).
There's some evidence in the numbers to suggest that Nokia has acted as a rising tide for all Windows Phone manufacturers. Non-Nokia Windows Phone device shipments doubled from 0.8 million to 1.6 million, a faster rate of growth than Nokia's own increase from 4.1 million to 7.1 million unit shipments.
There are multiple reasons for this, but one important factor is that operators generally express a preference for a multi-manufacturer ecosystems and will sometimes range a device to encourage this kind of manufacturer diversity. In the case of Windows Phone this will see an operator opt to carry a non-Nokia device (e.g. Samsung ATIV S or HTC 8S) as way of counter-acting the influence of Nokia's Lumia range.
IDC's numbers are drawn from their own research and checks in retail channels, but they are estimates, so should not been taken as absolutes. Numbers direct from the manufacturers, or from other research companies may be different. For example, Nokia, in its Q2 2013 results, indicated that it had shipped 7.4 million Lumia devices.