The search has begun to replace Gen. Rick Hillier, the outspoken chief of Canada's defence staff who announced his retirement on Tuesday.

Hillier, a strong advocate of Canada's military intervention in Afghanistan, said that he will step down in July.

"I have chosen to retire from the Canadian Forces and end my tenure as your Chief of the Defence Staff in July of this year," said Hillier, 52, in his resignation letter Tuesday.

Defence analysts say the search to replace him will be a top priority for the Harper government, which has faced criticism for its handling of the Afghan mission, and has reportedly had an occasionally rocky relationship with Hillier.

CBC's James Cudmore, reporting from Ottawa, says the next chief of defence staff is likely to be a serving general from the Canadian army, as Hillier was.

"There are a handful of generals at the top of the list," Cudmore said, "all from the army." 

Among them are Lt.-Gen. Andrew Leslie, the head of the army, Lt.-Gen. Michel Gauthier, who has spent the past two years helping to run operations in Afghanistan, and Lt-Gen. Walter Natynczyk, currently Hillier's second-in-command.

Job one of Canada's toughest:  Mackenzie

Lewis Mackenzie, a retired but still high-profile Canadian military officer, said the chief's job is one of the toughest in Canada.

"You're on call all of the time, and you're dealing with some of the most serious issues facing the country," Mackenzie said. "It's not just the army, you have your maritime patrols and your Arctic patrols and your search and rescue."

That aside, CBC's Cudmore said, the next chief will likely be from the ranks of the army, simply because of the demands of the current Afghan operation.

While the announcement of Hillier's departure from the job was a surprise, the general said he had been planning his departure since last fall.

"It's been a full day," a relaxed Hillier told a news conference in Ottawa Tuesday afternoon. But it was "not a surprising day from my perspective," he added.

When he was asked late Tuesday what his plans might include, Hillier told CBC News that "anything [else] will certainly be second-rate."

He dismissed speculation he might enter political life, but said, "I'll want an opportunity to contribute if I possibly can."

Good relationship with Harper:  Hillier

Before announcing his departure, Hillier said he had "several conversations" with Gov. Gen. Michaëlle Jean and Prime Minister Stephen Harper, and that he had also contacted Defence Minister Peter MacKay. As well, he said he'd heard from former prime minister Paul Martin, who appointed him in February 2005.

Harper told him there was "no hurry" for him to leave his post, Hillier said.

"The prime minister and I had a very enjoyable conversation," the general said, adding that "he understood that I had made my decision to depart at this time."

Hillier also denied that his leaving had anything to do with differences of opinion with the Prime Minister's Office.

"Disagreements are part of our life," he said, adding that he felt he had enjoyed a "positive" relationship with the PMO.

Last October, it was reported the Conservatives were seeking to push the outspoken senior military commander out of his job. But Harper denied the report, praising Hillier as an outstanding soldier and saying there had been no discussion about the possibility of changing the chief of defence staff.

A Martin appointee

The native of Newfoundland and Labrador has been in the job since February 2005, appointed by Martin. The role doesn't have a defined length, but the average tenure is three to five years.

Harper praised Hillier during question period on Tuesday.

"Gen. Hillier has worked very well with the government," said Harper. "He has done an excellent job in rebuilding Canada's Armed Forces. He is a great Canadian and we are proud to have worked with him."

In Kandahar, soldiers have been praising the outgoing chief of defence staff. Lt-Col. Dan Drew of the Princess Patricia's Canadian Light Infantry says Hillier was a personal friend.

"He stuck up for his men and he took us out of the dark ages of the '90s," Drew said. "He made us proud to be who we are and he made the Canadian people know who we are and proud of us again."

Master Cpl. Bob Gaudet echoed Drew's sentiments.

"He's been one of the pinnacle figures in the Canadian military and he's going to be missed, he's done a lot for us," Gaudet said.

Last fall, Hiller suggested that his work as defence chief was still unfinished. "I love being a soldier," Hillier said in October. "I still have things to do here in the immediate future, and I intend to do them."

Not one to mince words

Earlier this year, there was also a report that an angry Hillier called Harper over the government's handling of the Afghan detainee issue.

His blunt talk had also made headlines, for example, when he referred to the Taliban as "detestable murderers and scumbags."

He raised the ire of some Liberals when he described the period of budget cuts to the military that began in 1994 as the "decade of darkness." The remark prompted then Liberal defence critic Denis Coderre to refer to Hillier as a "prop to the Conservative party."

Last February, Hillier urged Parliament to come to a quick decision on the country's role in Afghanistan, warning that the longer the debate went on, the likelier the Taliban would "target us as a perceived weak link."

His own career has spanned three decades — he joined the army right after graduating from Memorial University.

Before being named chief of defence staff, he was the head of the army and also commanded the NATO-led multinational Afghanistan mission in 2004.