When Qatar made a sudden move to take the headquarters of a UN agency from Montreal, Canada launched into a no-delay, no-quarter campaign to beat it back. On Thursday, Qatar cried uncle and called Ottawa to say it was withdrawing its bid to win the seat of the International Civil Aviation Organization.

The Persian Gulf nation's audacious bid to move the seat of ICAO always required massive international support. But Ottawa saw it as serious: It quickly mustered domestic allies, dispatched MPs and ministers abroad, worked the phones for support, sent joint delegations with Quebec representatives and enlisted Quebec-based aerospace companies to lobby, too.

"We immediately and energetically put our full shoulders behind this wheel," Foreign Affairs Minister John Baird said in a telephone interview from Chicago. He said he always made it clear there would be no deal cut with Qatar for concessions – the country wants more landing rights in Canada for its airlines – and there was none.

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On Thursday, Qatari Prime Minister Sheikh Hamad bin Jassim bin Jaber Al Thani called Mr. Baird to tell him the fight was over. On Friday, Qatar officially withdrew. Canadian sources said Qatar's official diplomatic explanation was that it wanted to preserve its important relations with Canada, but they suspect another reason: Qatar had realized it would lose.

The quick, aggressive lobby to hang on to ICAO was different from a past example: the Harper government's listless 2010 campaign for a seat on the United Nations Security Council, which failed to quickly lock up potential supporters at a time when Canadian policy changes were alienating some nations in Africa and elsewhere – dooming a troubled bid.

But this time, with the headquarters of ICAO – which employs more than 500 people in Montreal – at stake, Mr. Baird quickly mounted a lobby, joined forces with the Quebec government and Montreal's mayor – and formed an improbable team with another politician with a combative reputation, Parti Québécois International Relations Minister Jean-François Lisée.

"We co-ordinated on a more-than-weekly basis, saying: Okay, we just heard this from that country, and that from this other country. We did our pointage [informal vote tallies] together," Mr. Lisée said Friday.

Mr. Baird called dozens of foreign ministers. His parliamentary secretary, Deepak Obhrai, was dispatched to a meeting of the African Union. Junior foreign minister Diane Ablonczy was preparing to lead a lobby with members of the Organization of American States. Canada's first call, to the United States, earned public backing, and France and Britain quickly offered support. Quebec aerospace companies lobbied foreign governments.

A first victory that may have persuaded Qatar to withdraw: The Gulf nation was trying to get ICAO's board of directors, at a meeting this week, to move the September vote on ICAO's headquarters from Montreal to Doha. Canada and Quebec lobbied the 36 countries on the board, and 32 refused to even allow that to be put on the agenda for this week's meeting, Mr. Lisée said.

From the start, Qatar needed to muster a lot of votes – 60 per cent of ICAO's members, or 115 countries. But it was serious, Canadian government sources said, and Ottawa was concerned the oil-rich country could use its largesse to help win allies. Countries at odds with Ottawa's political positions and aid cuts were expected to be lobbied.

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Some Arab nations, annoyed by Canada's vocal pro-Israel stand on Palestinian issues, were considering backing Qatar's bid. The Globe and Mail reported this month that UN ambassadors from Arab League countries had already devoted part of an April 23 meeting on Palestinian issues to countering Canada in international organizations; after Qatar announced its ICAO bid, some of those Arab nations were considering backing it because of Canada's Mideast stand, sources said.

Mr. Lisée said Arab nations didn't raise that with Canada-Quebec campaigners. "I wouldn't be surprised if Qatar would have used this argument in their campaigning, but the Arab world didn't tell this to us. We couldn't have a good count of the Arab world on this issue because they were very prudent," he said.

Mr. Baird said Canada's Mideast policy was not a significant factor and that private talks indicated "strong support, including from Africa and the Middle East.

"Qatar would seek support from their close friends and neighbours as well," he said. "We didn't get unanimous support, but we got strong support."