KANDAHAR, Afghanistan - Maj. Rob McKenzie was south of Nakhonay, a notorious Taliban redoubt in Kandahar, when a rocket-propelled grenade plowed into the ground and exploded near his tank -- the first time his squadron of Leopard 2 A6M tanks had come under direct fire.

McKenzie had a pretty good idea where the round had come from, and scanned the parched fields around him from within his 62,000-kilogram iron monster, one of several summoned to help cover a company of sweaty, exhausted infantry that was coming under heavy Taliban fire.

"My gunner was looking somewhere else, but I had my (targeting sites) up looking, and buddy stepped out into the gap again with an RPG on his shoulder," said McKenzie, 48, commander of A Squadron of the Lord Strathcona's Horse (Royal Canadians) regiment based in Edmonton.

It was one of those moments when time slows down.

"Bugger looked me right in the eye and pulled the trigger," McKenzie recalled with a chuckle.

That brazen shot, too, landed in the dirt.

But it taught the 48-year-old McKenzie, a native of Bellbeck, Sask., some important lessons as his tour began in May of this year. First and foremost, his troopers faced hardened, disciplined fighters. Second, tanks are important.

"That will always stand out in my mind," said McKenzie, who finally goes home this week along the with rest of his troops, who are being replaced by members of the 1st Battalion of the Quebec-based Royal 22e Regiment.

At the same time, the Canadian army is taking the opportunity to return some of the tanks it hastily borrowed from Germany more than three years ago as the war was exploding in the withered farmland west of Kandahar city.

The heavily armoured Leopard 2 A6Ms were rushed into Kandahar in the summer of 2007 to help defend troops against bigger and more powerful roadside bombs.

Fewer than half a dozen of the 20 borrowed machines are being replaced with upgraded Leopard 2 A4M tanks, which the Defence Department purchased from the Dutch and modified for use in Afghanistan's arid desert, said Lt.-Gen. Peter Devlin, the head of the army.

All of the borrowed vehicles will be returned after the combat mission ends next spring, and will have to be refurbished before they are returned, Devlin said in a recent interview.

"The ones going now are part of the normal replacement, based on hours and mileage."

Various squadrons from the Lord Strathcona's Horse have rotated in and out Kandahar since tanks were first rushed into theatre following the bloody compound-to-compound fighting of Operation Medusa in 2006.

That was when Canadians led the fight in the volatile province that spawned the Taliban movement.

There has been furious debate over the years in the defence community about whether tanks are necessary or even counter-productive in a counter-insurgency war where the objective is to win over the local population.

Ordinary infantry complain about the tanks all the time, and dismiss their importance with jokes.

"Tanks are like the fat, slow kids you pick last to be on your team. They're there and you gotta have 'em," one unidentified soldier cracked on his way home after a six-month rotation with the Petawawa, Ont.-based 1st Battalion of the Royal Canadian Regiment battle group.

None of the U.S. battalions now operating in Kandahar brought tanks with them, despite the Canadian experience, which showed the Leopards have minimized casualties and forced the Taliban to keep their heads down.

Members of the Lord Strathcona's Horse, which operated in the Canadian sector of Panjwaii, were seconded to the Americans last month to help with NATO's big offensive through western Kandahar.

McKenzie said he values "the mobility, the protection, the deterrence that tanks afford, and the message you send to the insurgents."

"If tanks roll up, they know you mean business. If that makes them turn around and leave in the opposite direction, then you've accomplished the aim without firing a shot."