I need to mention that as of mid-July when this post was drafted, his Wikipedia entry was flawed. A short, better biographical sketch is here.
It seems that Johansen originally painted landscapes before focusing on portraits of men -- probably a more lucrative artistic pursuit. Most of the examples I found on the Web were works related to his commission to portray the 1919 Versailles conference that concluded the Great War. These portraits tended to be competently made, though their colors were rather drab.
This was used as cover art for a recent biography of Wilson. I like the way Johansen blocked in Wilson's head and facial structure.
He painted several portraits of his Stockbridge, Massachusetts summertime neighbor who is best known for sculpting the seated Lincoln in the Washington DC Lincoln Memorial.
What he was sent to France to portray.
French wartime Prime minister.
Joffre, now a Marshal of France, led French armies during the first years of the Great War. His most important accomplishment was realizing that his prewar Plan XVII was a failure, then repositioning his forces to defeat the German armies in the Battle of the Marne in early September 1914.
Similar pose to Johansen's, though details differ. I have no idea if there was any connection between these two works.
Diaz assumed command of Italy's army after failures by his predecessor and was successful against German and Austro-Hungarian forces.
Probably painted circa 1910.
Like the Versailles scene above, Johansen often liked his subjects low, below tall windows. Note the brighter coloring than the portraits above.
M. Jean McLane (1878-1964), Wikipedia entry here, was Johansen's wife and also a portrait artist.