Law enforcement officials plan to announce charges Thursday against a dozen members of the Turkish president’s security detail for their involvement in a brutal attack on protesters outside the Turkish ambassador’s residence here last month, two American officials said on Wednesday. Authorities have already charged several others, including two Americans and two Canadians, with taking part in the violent skirmish. The Washington police have been investigating the May 16 incident along with the State Department and the Secret Service. The police planned to announce the charges at a news conference on Thursday morning, according to the two officials, who spoke on the condition of anonymity to discuss the charges before they were made public.

Washington police officials confirmed that the two Americans are Sinan Narin, of Virginia, and Eyup Yildirim, of New Jersey. Mr. Narin was charged with felony and misdemeanor assault. Mr. Yildirim, who can be seen on video repeatedly kicking a protester, was charged with two felony counts and one misdemeanor assault count. The two have been arrested….

Coming almost a month after the incident, the charges are the most significant retaliatory step taken to date by American authorities, who have fumed privately and publicly over what they see as a highly offensive attack on free speech — not to mention American law enforcement.

Lawmakers from both parties on Capitol Hill, as well as a smattering of advocacy groups, have clamored that those responsible for the assault be prosecuted. Last week, the House unanimously passed a resolution condemning the attack and calling for charges against the security forces. In calibrating its response, though, the Trump administration has had to tread carefully, navigating a web of diplomatic and military concerns with a key NATO ally. The incident appears to have already stalled a proposed $1.2 million small-arms sale to Turkish security forces that was moving toward approval by the State Department last month.

And then there was the added wrinkle that the entire security detail for President Recep Tayyip Erdogan of Turkey had left the country with him just hours after the incident. Members of the security team face several felony and misdemeanor counts, the American officials said. It is highly unlikely that Turkey would extradite the men to the United States to face the charges, but they do face the possibility of arrest should they ever try to re-enter the country.