What is hybrid warfare, which some fear Russia will use after Ukraine’s strike?

Strike with US-made missiles has prompted fears of Russian reprisal that would broaden the scope of a frontline

A Ukrainian strike using American-made missiles to hit targets deep inside Russia using American-made weaponry, has prompted renewed fears of reprisal through hybrid warfare" - a chaotic tool of conflict that muddies borders and broadens the scope of a frontline.

Over recent years, European nations have witnessed a spate of incidents - cyber-attacks, arson, incendiary devices, sabotage and even murder plots. The aim of such episodes, security officials believe, is to sow chaos, exacerbate social tensions among Ukraine's allies and disrupt military supplies to Kyiv.