Ernest Hemingway traveled to Madrid in March of 1937 to observe the Spanish Civil war firsthand. He reported on the war for the North American Newspaper Alliance. In March 1937, he traveled to Madrid to observe conditions firsthand. His observations and experiences provide the inspiration for the novel.
The Spanish Civil War lasted from July 1936 - ...
Unfortunately he did not, though it's a great thought!
According to this excerpt from a 1997 interview he did on the DragonCon SciFi Channel Chat (yah, before the name change):
What made you decide on Robert Jordan as your pseudonym? Is it Hemingway?
No, it wasn't Hemingway. I simply wanted to separate the different kinds of books ...