In July of 1914, before war was even declared, R.B. attempted to enlist for service. Somewhere between his age, forty-four years old, and his physical health, he was turned down. He did, however, find other ways to help. He accepted an invitation to become part of the Alberta Red Cross and soon became the president. He worked diligently and in 1919 represented Canadians at an international medical conference in Cannes, France, where the Canadian Red Cross was recognized as an independent National Society of the Red Cross. He also became a board member of the Southern Alberta Patriotic Fund, which raised money in support of the families of the fighting men.
R.B.'s mother, Henrietta, died on October 1, 1914 at the age of seventy. Evelyn, now a schoolteacher, and Mildred, a recent graduate from Mount Allison University, were both living at home with their mother when she died. R.B. returned to Hopewell Cape to look after matters and help the family through the difficult period.
In 1917 the Robert Borden government faced several difficult issues as a result of World War One. The final straw was the conscription crisis that resulted in another election. R.B. had already made up his mind to leave politics (again) and spoke to Borden on the matter. R.B. left the meeting with the expectation of a Senate appointment. But, R.B. could not ignore the matter of the day and criticized his own party's handling of the conscription issue among other things. When all was said and done R.B. was passed over for a Senate seat. To top it off, he had, in anticipation of a Senate appointment, not placed his name in nomination for re-election in 1917. R.B. was out of parliament completely.
On July 10, 1920, Robert Borden visited the Governor General of Canada and stepped down as prime minister. Arthur Meighen, Borden's successor as leader of the Conservative and the Unionist Party, was asked to become the next prime minister.
In May of 1921, finding himself in a perilous political environment, Meighen wrote to R.B., an old rival, and asked him to join the government as a cabinet minister. R.B. said no. Meighen pleaded again with another offer and before R.B. had the chance to answer, a third offer was made. R.B. accepted the third offer to become the minister of justice. He served as Canada's minister of justice even though he did not have a seat in the House of Commons. This meant that he could not participate in committee work, vote, or appear at question period. After six months, due to a resignation, R.B. also took on the position of attorney general.
A general election was called for December 6, 1921. R.B. was at first declared the winner in his riding by 6 votes. A recount was naturally requested and voting irregularities were found. R.B. had actually lost the seat by 16 votes. He appealed the decision all the way to the Supreme Court of Canada but the results were found to be the same. Besides R.B. losing his riding, Meighan's Conservatives were trounced by the Liberals under the leadership of William Lyon Mackenzie King.