This crisis is far different from the one in Mali, another former French colony, where France intervened militarily in January to halt an advance by Islamist insurgents.

“In Mali you had a pretty identifiable enemy in one part of the country, albeit a large part, but in the Central African Republic you have communities breaking into violence all over the country — it’s not just one group,” said a Western diplomat familiar with the situation, who asked not to be named because of he was not authorized to discuss the situation with reporters.

The full contingent of 1,600 French troops arrived over the weekend, and the United States is now helping to transport reinforcements from other African countries to join an African Union force of about 2,500 soldiers already deployed, with the goal of increasing that force to 6,000. The soldiers are authorized to pre-empt violence under a United Nations Security Council resolution approved last week. President Obama has ordered $60 million in nonlethal military equipment to be sent.

It is unclear whether that will be enough.

“What we are facing today is a bit heavier than we expected,” said a French diplomat speaking in Washington this week, referring to some of the Muslim militias active in Bangui and elsewhere. “We plan for everything,” said the diplomat, who, under the diplomatic protocol established by the French government, declined to be identified. “But some have hidden weapons in the capital city and are behaving in a very unconventional way with fake uniforms. Some are wearing civilian clothes. We have to cope with that; we hope we can.”

The genocide in Rwanda in 1994 casts a long shadow. The French have been blamed for not doing more and accused of allowing the escape of some notorious figures who were involved in perpetrating the carnage, and they now appear committed to preventing a similar cycle of killing.