You have to admire the courage of war correspondents, the journalists who place themselves in the middle of a conflict in order to bring us reports of the fighting and destruction and its effects on citizens. In December 1936, six months after the start of the Spanish Civil War, George Orwell travelled to Spain "with some notion of writing newspaper articles". Unlike today's reporters he went a step further. He promptly joined the militia, "because at that time and in that atmosphere it seemed the only conceivable thing to do". It's rather a lame explanation, ill-considered and reckless considering what happened next.
Orwell describes his experiences in Homage to Catalonia. He patrolled the front line with the militia in Aragon, defended Anarchist positions in Barcelona, was shot through the neck, and managed to safely escape with his wife to England. His descriptions of trench life, fighting and hiding in full view are excellent. How would you know, unless you'd experienced it, that "When an aeroplane swoops down and uses its machine-gun the sound, from below, is like the fluttering of wings", or that being shot is painless? A number of times he admits to fear, and that there's very little glory in fighting. It's above all "mud, lice, hunger, and cold."
On reflection it must have been a seminal experience for the writer, and one that produced his two most revered works of fiction. In one episode the militia spent a night in a barn that Orwell says was "alive with rats. The filthy brutes came swarming out of the ground on every side. If there is one thing I hate more than another it is a rat running over me in the darkness." It reminded me of the dreaded Room 101 in 1984.
Orwell's attempts to explain the politics and the different factions of the conflict are less convincing and there's a naivety in his support for the Anarchists and their ideology. He warns "against my bias, and ... against my mistakes.", aware that "One of the dreariest effects of this war has been to teach me that the Left-wing press is every bit as spurious and dishonest as that of the Right." The Daily Mail comes in for much criticism, and the only newspaper to escape is the Manchester Guardian.
If you want to understand the background to the Spanish Civil war it's probably best to read Homage to Catalonia in conjunction with more expert studies (I started with an article by historian Paul Preston but innumerable histories have been written in the 70 years since the conflict).