The United Nations on Friday conceded that an attack that killed 15 peacekeepers in the Democratic Republic of Congo late last year exposed "gaps" in how UN troops are trained.
The December 7 attack in the Beni territory of North Kivu province was one of the worst to target UN peacekeepers in recent history in the country.
Fifteen Tanzanians were killed and 43 other peacekeepers wounded.
It was the bloodiest attack against MONUSCO, the UN force deployed in DR Congo since 1999, and the worst against a UN force since the death of 24 Pakistani peacekeepers in Somalia in June 1993, leading to a special UN investigation.
UN investigators were tasked with evaluating the response of the UN peacekeepers and making recommendations on how to prevent such violence.
"The team found a number of gaps in the training and posture of MONUSCO and its Force Intervention Brigade," the United Nations said in a statement Friday.
"Moreover, the investigation team noted that the mission did not have an actionable contingency plan to reinforce and extract its peacekeepers during the attack.
"Issues of command-and-control, leadership and lack of essential enablers such as aviation, engineers and intelligence were also major obstacles and need to be addressed urgently," it added.
UN Secretary-General Antonio Guterres had appointed Dmitry Titov, a Russian who has worked in UN peacekeeping, to lead the special investigation.
The United Nations had said the ambush was carried out by suspected ADF rebels, a shadowy group dominated by hardline Ugandan Muslims that is one of several armed groups active in the North Kivu region.
Citing the conclusions of the investigation, the world body said Friday that "all available evidence" pointed to the ADF as the culprits.
A UN report made public last month recommended that UN peacekeeping forces change the way they operate and not shy away from using force to reverse a worrying trend of escalating fatalities.
DR Congo's east has long been wracked by violence, but fighting between government soldiers and militia groups, as well as inter-ethnic clashes, increased in 2017.