"Of course casualties are something that we have to expect when we are involved in these operations, and people have had that brought home to them," he said.
"This is not in any way a safe environment and it doesn't matter how much kit and equipment we provide for people, we can never entirely make these operations risk-free.
"But they are well planned and there is good provision and we can only hope for success for our people in bringing that relief for the Afghan people and the Afghan countryside.
"People will do everything they can to minimise casualties and it is at the forefront of the minds of the people that plan all of our operations.
"But we shouldn't deny ... casualties are a very real risk on these types of operations and people have to be prepared for that."