Dhaka, March 16 -- Tens of thousands of Italians gathered in central Rome on Saturday, waving European Union flags in a show of unity as debate intensifies over the EU's push for increased defense spending.

The rally, backed by most center-left opposition parties despite their differing stances, was initiated by Italian journalist Michele Serra. His call for action came in late February through an editorial in La Repubblica titled "Let's say something European."

"My goal was to organize a major demonstration of citizens in support of Europe-its unity and its freedoms-without party banners, only European flags," Serra said, coining the slogan: "Here we make Europe, or we die."

The movement emerged as a response to escalating tensions be...