Little green men

The phrase "little green men" refers to masked soldiers of the Russian Federation in unmarked green army uniforms and carrying modern Russian military weapons and equipment who appeared during the Russo-Ukrainian War in 2014.

The term first arose during the annexation of Crimea by the Russian Federation, a period from late February to March 2014, when such forces occupied and blockaded the Simferopol International Airport, most military bases in Crimea, and the parliament in Simferopol.

Russian media referred to them with the euphemism "polite people".The Russian Federation initially denied that these were Russian military forces, but on 17 April 2014 Russian President Vladimir Putin finally confirmed the presence of the Russian military.

Source: Wikipedia