One aspect of modern warfare that is new is the atomic bomb. It was used only once—at the end of World War II. The United States used it to bomb the Japanese cities of Hiroshima and Nagasaki in 1945; nearly all of the victims were civilians. At the time, the US was the only nation to possess nuclear weapons. As of 2020, nine countries have them. Today, atomic bombs are considered so dangerous that countries are loath to use them. A terrorist group, however, would have no qualms about using one.
Another weapon developed toward the end of WWII was the missile. Germany used them to attack civilian targets in Britain in 1944–45. The missiles used in 2020 are much deadlier. Some military analysts believe that missiles render aircraft carriers obsolete.
Drones, essentially flying robots, may be the future of aerial warfare. They are widely deployed today, and they are becoming more sophisticated and lethal every year. The United States used one to killed an Iranian military leader in January 2020. Although America's military has typically used a single drone to eliminate a target, drone swarms are likely to be used in the very near future. A drone swarm overwhelms the air defenses of a target.
Another characteristic of modern warfare is the extensive use of small groups of elite forces. For example, Osama bin Laden was killed by American special forces in 2011. The huge armies of WWII and the Napoleonic era seem to be a thing of the past. Instead, small groups of soldiers with advanced technology are increasingly used.