"arduous mission" is a correct and usable phrase in written English.
It describes a difficult and challenging task or assignment. Example: "The team was assigned the arduous mission of climbing to the summit of Mount Everest in record time."
Then, in late June, Colonel Blakeslee led his fighters on one of their most arduous missions, escorting shuttle-bombers to Russia.
For La Cañada, another new coach has his team looking to challenge for the Rio Hondo League title, while Flintridge Sacred Heart Academy will field a youthful squad looking to compete in the ever arduous Mission League.
For Crescenta Valley, a team filled with seniors and a sensational sophomore returner is hoping to challenge for the Pacific League title, while Flintridge Sacred Heart Academy will field a youthful squad looking to compete in the ever arduous Mission League.
The Lions will need plenty of those qualities in Australia, something beaten Barbarians coach Dai Young - part of the 1989 and 2001 Lions tours down under - felt would be a by-product of this arduous opening mission.
As he got to know people who embarked upon the arduous, isolated missions — some for months on end — he found them "super, super serious" about paving the way for future explorers, as one man in his 80s put it.
I know they will be uppermost in our minds and prayers as we take on this arduous but vitally necessary mission.
Clinton was in the room for the most important calls of her tenure, including the arduous planning of the mission to kill Osama bin Laden.
Before, Mexicans had to return to their birthplace to obtain the document, or ask relatives to lobby on their behalf – both arduous, expensive, time-consuming missions.
However, given the arduous training required for his mission, Tito objected to the use of the word tourist, and since his flight the term spaceflight participant has been more often used to distinguish commercial space travelers from career astronauts.
