What is the S-400 missile system?

The US State Department has urged Turkey to dispose of the Russian-made S-400 missiles in its arsenal, warning that its continued dealings with Vladimir Putin’s regime could result in fresh sanctions under a federal law known as the Countering America’s Adversaries Through Sanctions Act (CAATSA).

Recep Tayyip Erdogan’s government was previously sanctioned by the Donald Trump administration when it signed its initial deal to acquire S-400’s from Russia in 2017, taking delivery two years later.

The matter returned to the international spotlight on Tuesday when Turkish defence minister Hulusi Akar told Ankara’s Parliament that the country would be prepared to use the air defence rockets should its territory come under attack.

“We have no problems with the S-400,” Mr Akar said.

“The S-400 is in place and ready for use. It has a transfer time. After that, everything will be ready in an hour.

“If such a threat develops in any way, we will take it and use it after deciding where our country’s air defence will be.”

But a State Department spokesman argued that Turkey’s use of the weapons was inconsistent with its commitments as a Nato ally and directly contravened a summit resolution agreed in Warsaw in 2016 that members should reduce their dependence on the Russian defence industry as punishment for Mr Putin’s annexation of the Crimean Peninsula in 2014 and his alleged fostering of separatist tensions in Ukraine’s eastern Donbas region thereafter.

That conflict proved to be the prelude to the all-out invasion of Ukraine the Kremlin launched in February this year, which the likes of Turkey risk bankrolling by continuing to buy weapons from Moscow, the American official said.

The S-400 air defence system in question is a mobile, long-range, surface-to-air weapon first developed by Russia in the 1990s as a successor to the S-300.

It was brought into service for the first time in February 2007 and first used the following August.

According to Army Technology, the truck-mounted system “integrates a multifunction radar, autonomous detection and targeting systems, anti-aircraft missile systems, launchers, and command and control centre”.

The S-400 is reportedly capable of firing three types of missiles, giving it a high degree of versatility as a defensive weapon.

It is commonly used to down aircrafts, unmanned drones and ballistic and cruise missiles within a range of 400km and at an altitude of up to 30km and is capable of engaging 36 targets simultaneously.

Both Russian and Ukrainian defence officials have recorded the aggressor making use of it to fire on Ukrainian aerial targets during the current war.