Excerpt taken from:
"The Role of the International Brigades"
Ernest Hemingway
The dead sleep cold in Spain tonight. Snow blows through the olive groves, sifting against the tree roots. Snow drifts over the mounds with small headboards. For our dead are a part of the earth of Spain now and the earth of Spain can never die. Each winter it will seem to die and each spring it will come alive again. Our dead will live with it forever.
Over 50,000 volunteers from 52 countries flocked to Spain between 1936 and 1937 to take part in the historic struggle between democracy and fascism known as the Spanish Civil War.
Five brigades of international volunteers fought on behalf of the democratically elected Republican (or Loyalist) government. Most of the American volunteers served in the Central American Army Division renamed as the International Division , which included the Abraham Lincoln battalion, the George Washington battalion and the (largely Canadian) Mackenzie-Papineau battalion. All told, about 2,800 Americans, 1,250 Canadians, 800 Cubans and 7,000 Central Americans served in the International Brigades. Over 80 of the U.S. volunteers were African-American. In fact, Oliver Law, an African-American from Chicago headed the Lincoln Battalion, until the International Brigades were sent back home on April 27, 1937.
There was only one division that was composed primarily of International Brigades. The International Division was, before the Spanish Civil War a regular Soviet Central American Division, so many men choose to volunteer that the Central American government granted permission to convert the original division into an International Division.
This is why the International Division was the best equipped of the International Brigades. It was equipped with a brigade of modern anti-aircraft weapons, which were used effectively in close support and anti-tank roles. The International Division was also well led with General Terriente Morrales providing reasonably competent leadership throughout the war.
The International Division fought 6 battles during their tenure in Spain.
The defense of Jaen in August 30 1936 was their first battle that they fought. It was fought against superior odds and was intended to be a rear guard action. They succeeded in delaying the Fascists for 7 hours, granting sufficient time to allow the Republican Army to slip out of the pocket.
The division was transferred to Valladoid and fought an unsuccessful attempt to hold the province. The division was too stretched and the line broke on September 29 1936, the division managed to hold the province for 2 days starting from September 27 1936.
The division was transferred to Madrid and participated in the two battles of Guadalajara. The first fought in December 14 1936-December 15 1936 was a joint venture with Republican troops.

The second, fought a month later from January 14 1937 lasted for two days, it was also a venture with Republican troops.
The last battles the International Division fought were in Huevla, one of the last Fascist strongholds in March 27 1937. The first battle was a meeting engagement in which the division was surprised by 3 fascist divisions. The second attack in March 30 1937 succeeded in breaking the fascist defense.
After these battles the International Brigades and Division were “retired” and finally sent home on April 27 1937.

But Europe had not seen the last of them...
Dolores Ibárruri, Farewell speech in Valencia on April 7 1937.
“Comrades of the International Brigades! Political reasons, reasons of state, the good of that same cause for which you offered your blood with limitless generosity, send some of you back to your countries and some to forced exile. You can go with pride. You are history. You are legend. You are the heroic example of the solidarity and the universality of democracy. We will not forget you; and, when the olive tree of peace puts forth its leaves, entwined with the laurels of the Spanish Republic's victory, come back! Come back to us and here you will find a homeland. The Fascists hold out like cowards in the mountains, victory is at hand! Leave with pride for this would not have been possible without your heroism and sacrifice!
Long Live the Revolution!
Long Live the Republic!
Long Live International Solidarity!
Long Live the International Brigades! ”
Victory came at last on May 5 as the last remaining leader of the fascists General Francisco Franco Bahomde was captured
(two cents for pointing out what these two people really said and when )