I can think of three examples.
(1) Russian Revolution (February 1917)
Driven by shortages of food and fuel, crowds of hungry citizens and striking workers began spontaneous rioting and demonstrations. Local reserve troops, called in to suppress the riots, refused to fire on the crowds, and some soldiers joined the workers and other rioters
http://www.russiansabroad.com/russian_history_52.html(2) Have heard/read that soldiers in WWI were at the brink of mutiny
Futile attempts at frontal assault—with a rigid adherence to unimaginative maneuver—came at a high price for both the British and the French poilu (infantry) and led to widespread mutinies especially during the time of the Nivelle Offensive in the spring of 1917. News of the Russian Revolution gave a new incentive to socialist sentiments among the troops, with its seemingly inherent promise of peace. Red flags were hoisted, and the Internationale was sung on several occasions. At the height of the mutiny, 30,000 to 40,000 French soldiers participated.
...Meanwhile, news of Germany’s impending military defeat had spread throughout the German Armed forces. The threat of general mutiny was rife.
http://en.wikipedia.org/wiki/World_War_I(3) Have heard/read that soldiers in Vietnam were at the brink of mutiny
THE MOST neglected aspect of the Vietnam War is the soldiers' revolt -- the mass upheaval from below that unraveled the American army. It is a great reality check in an era when the U.S. touts itself as an invincible nation. For this reason, the soldiers' revolt has been written out of official history. Yet it was a crucial part of the massive antiwar movement whose activity helped the Vietnamese people in their struggle to free Vietnam -- described once by President Johnson as a "raggedy-ass little fourth-rate country" -- from U.S. domination. The legacy of the soldiers' revolt and the U.S. defeat in Vietnam -- despite more recent U.S. victories over Iraq and Serbia -- casts a pall on the Pentagon. They still fear the political backlash that might come if U.S. ground forces sustain heavy casualties in a future war.
http://sf.indymedia.org/news/2002/10/1537457.php(This thread was inspired by the thread,
at what point will rank-and-file soldiers refuse to be cannon fodder for a madman?
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=364x3035917 )