The civil war was marked by the extensive involvement of international units. Many joined the Republican side under the banner of the International Brigades. The Nationalists enjoyed support from Nazi Germany and Fascist Italy, with several new technologies being trialled as a result. The Nationalist side conducted aerial bombing of cities in Republican territory, carried out mainly by the Luftwaffe volunteers of the Condor Legion and the Italian air force volunteers of the "Corpo Truppe Volontarie" – the most notorious example of this tactic of terror bombings was the bombing of Guernica. The first combat use of the "Stuka" occurred during the conflict. The civil war influenced European military thinking on the alleged supremacy of the bomber. Armoured warfare was also trialled by Nationalist supporters; German volunteers first used armor in live field conditions in the form of the Panzer Battalion 88, a force built around three companies of PzKpfw I tanks that functioned as a training cadre for Nationalists.