British troops have destroyed a Taleban training camp in southern Afghanistan, killing dozens of insurgents, according to the military.
Many Taleban fighters are thought to have been killed in the operation
About 110 Royal Marines carried out the operation in northern Helmand, which it is hoped will pave the way for repairs on a hydroelectric dam in the province.
It is hoped nearly two million people will now get access to electricity.
Operation Clay was launched on New Year's Day. Plymouth-based 42 Commando were engaged in four days of fighting.
Afghanistan's President Hamid Karzai has thanked Operation Clay's commanders.
Mr Karzai, who is championing the scheme to fix the Kajaki Dam, sent a personal message.
A senior Taleban commander and "tens" of his fighters are said to have been killed during the operation.
Only one marine was hurt during the battles. The soldier was shot through the hand.
Insurgents had been stalling repairs on faulty turbines at the dam, which is situated at the source of the Helmand River.
Repair work on the facility, which was built in 1953, will now commence next month.
It is estimated it will bring electricity to about 1.8 million people and treble the area of irrigated farmland in the fertile province.
Military spokesman Major Oliver Lee said: "We needed to sort out the insurgency that there has been in the environs of Kajaki.
"And we very successfully did that over this past week or so with some very focused targeted military operations, which included killing the key insurgency commander at that location."
He said there had been "running firefights" for up to four days against "fairly coherent sustained attacks of small arms, rockets and indirect fire".
Maj Lee said he believed the operation, which had the support of the Afghan National Police, could also boost their campaign against the Taleban fighters in the province.
He said: "I would suggest that we have significantly seized the initiative from the irreconcilables in that area."