What are HARM, the air-to-surface missiles destroying Russian air-defence radar?

ON AUGUST 19TH a senior Pentagon official confirmed what had previously only been hinted at: America is supplying Ukraine with High-speed Anti-Radiation Missiles (HARM). The missiles have been playing an important role in Ukraine’s spectacular offensive in Kharkiv province, as well as a separate attack in the south. Launched from an aircraft, HARM homes in on and destroys air-defence radar. The missiles represent a serious challenge to Russia. Even if not fired, the threat they pose can force radar operators to turn off their sets and lie low. Ukraine’s air force, as a result, may not quite fly with impunity, but it has greater freedom than before.

During the second world war batteries of large-calibre anti-aircraft guns were deployed to counter bombers, but these became obsolete once jet bombers could fly faster and higher. Missile technology responded, and by the late 1940s the first radar-guided surface-to-air missiles (SAM) appeared. These evolved rapidly and could soon reach stratospheric altitudes and bring down the fastest jet. Bomber crews then had to learn to fly under the radar, or find ways of countering it, such as jamming by electronic warfare.