The Prime Minister told delegates in New York that Britain is 'going to increase further our security support' in Somalia.
What she was announcing was a £7 million deployment of British training personnel to the East African country which is fighting al-Shabaab extremists.
A total of thirty training teams will be sent to Somalia and will be deployed in and beyond the capital Mogadishu.
A Downing Street spokeswoman said that no more than 70 British personnel would be in the country at any one time.
They will all be used to train the Somali national army - rather than fight the Islamist extremist group themselves.
The decision may well have been taken by David Cameron had he remained in Number 10 - so it would be wrong to read this deployment as Theresa May big new focus on the world stage.
Neither is it right to say that Somalia will be the 'new Afghanistan' or 'new Iraq' for British forces.
Nevertheless, it's an indication that Mrs May wants to try to contain the extremist group - and deny it the space to grow and become a greater security threat beyond Somalia's borders.
It reflects a desire by the new Prime Minister to build up the capacity of the government forces in that country.
As recently as last weekend, al-Shabaab militants said they detonated a car bomb which killed an Army general and four of his guards in Mogadishu.
At the end of August, an al-Shabaab suicide bomb killed 20 people.
The group has also called on its followers to kill parliamentarians taking part in next month's elections.
Theresa May will convene an international summit in London on Somalia and direct £20 million from Britain's aid budget to help Somalia refugees in Kenya return home.