Officials say the move will make the force more efficient, as it seeks to secure Afghanistan for reconstruction.
Some 10,000 US troops have come under the command of Gen David Richards from the UK.
The addition of US troops brings the total number of troops under Nato command in Afghanistan to about 31,000.
This is good news, and represents a major step forward for NATO. A successful mission in Afghanistan (which is still not guaranteed) will boost the organisation’s credibility.
The cynic in me does wonder, though, just how effectively a British general will be able to ‘command’ US troops in practice. I’m sure many of NATO’s member states will be watching with interest to see how well the US adapts to putting such a large number of its troops – who are currently engaged in combat missions – under the command of a foreign general.