Operation Domino

Operation Domino was a disasterous operation made by the Alliance to Restore the Republic during their initial struggles against the Empire. It's premise was to call in the stronger Sector Forces to defeat local Imperial Army garrisons in showpiece battles and then dig in behind their planetary shields with the intention of proving that planets could free themselves and thus inspire revolution across the galaxy. However, it backfired in that it caused the various uprisings to meet crushing defeat from the Empire, resulting in there being no revolution, dozens of Alliance armies destroyed, and surviving units fleeing. It was because of this that one of the leaders, Mon Mothma, learned that while having a hundred Sector Forces would muster infantry brigades, its only part of an army: Most of the soldiers lacked formal training, while some lacked bases, and others lacked air support or spare parts.

Behind the scenes
According to Paul Urquhart in Jason Fry's endnotes of The Essential Guide to Warfare, the name of the campaign was derived from the "domino theory," a theory dating back to the Vietnam War-era regarding the likelihood that Communism will run rampant across Southeast Asia and other regions if left unchecked. He also noted that the event itself was first mentioned in the Rebel Alliance sourcebook, although he isn't sure if the name came from the source or if he named it himself.