Starlink satellites operated by Elon Musk’s SpaceX provide high-speed internet – something modern war relies heavily on.

For Ukraine, it is vital for communications on the battlefield and effective drone warfare.

Using Starlink, Ukrainian drones can stay connected to operators over longer distances than conventional radio networks and are less vulnerable to jamming.

But on Tuesday night, Starlink suddenly and unexpectedly restricted the speed at which drones could fly while still maintaining internet connection. This disrupted some battlefield “missions”, a top Ukrainian official said, and hampered Kyiv’s ability to protect itself from incoming Russian attacks.

The restriction at 100mph (160km/h) meant that any drone travelling faster than that lost connection and was effectively useless.

“Starlink gives Ukraine the ability to see what’s coming, to protect people,” Kurt Volker, former US ambassador to Nato, told the BBC’s Radio 4 Today programme. “If you cut that off, then more people are going to get killed – and that is a very cynical and callous decision to slow that down the way that has been done.”

Connectivity had been restored by Wednesday evening.

The move has once again shown how Starlink can impact the conflict, which has been raging since Russia launched its full-scale invasion of Ukraine in February 2022.

Starlink is an internet network that uses satellites in low Earth orbit to provide connectivity, particularly in remote areas and battlefields.

It currently relies on more than 10,000 active satellites, making Starlink the world’s largest satellite constellation.

It is owned by Elon Musk’s SpaceX, and is the company’s biggest revenue driver.

While Starlink is for civilian use, Starshield is its military-grade service, designed for use by the Pentagon.

Starshield relies on the Starlink network, but has greater security like enhanced encryption so that sensitive information can be transmitted without interception.

The US government has allowed Ukraine to use Starlink and Starshield in its defence against Russia. Musk cut Moscow’s access to the service in February, giving Kyiv an advantage in the conflict.

Put simply, Starlink uses its thousands of satellites to ping high-speed internet back to almost every corner of the globe, using terminals on the ground that users can easily buy and set up themselves. As Musk said, they have two instructions: “point at sky, plug in”.

This makes them ideal for use on the battlefield.

“It’s a connection… that you can basically use pretty fast, you don’t need any special equipment, you don’t need to prepare, you just go to the field and usually it works,” Neo, a soldier with one of Ukraine’s drone reconnaissance units, told the Today programme.

The network has become “the backbone of military communications in Ukraine”, George Barros from the Institute for the Study of War (ISW) said, and is used across Kyiv’s naval, land, and air forces.

In Ukraine, both Starlink (the civilian service) and Starshield (the military service) are used, depending on what communications are needed.

It is crucial for the effective use of weapons such as drones, which connect to the network so that operators can see their targets in real time.

The technology effectively allows “drones, artillery and command posts to function as a single real-time network where the time between sensor-to-shooter is minimised,” Barros, who is the ISW’s Director of Innovation and Open Source Tradecraft, told the BBC.

Ukraine also relies on the Starlink network to protect its own skies against incoming Russian attacks, especially jet-powered Shahed drones, Barros said.

Shaheds fly at speeds in excess of 198mph (319 km/h), meaning SpaceX’s restriction makes Ukrainian efforts to chase them down all but impossible.

With no ready replacement for the Starlink network, any speed restrictions or loss of connectivity have major implications for Ukraine defences, and the recent limits have shown how dependent Kyiv is on the network.

While Starlink can provide access nearly everywhere in the world, that does not mean it can be accessed everywhere, and countries must be licenced to use it.

Russia is one place where it is not authorised, although Kyiv has in the past said that Moscow was still getting hold of the terminals and using them in occupied territory in Ukraine.

“If SpaceX obtains knowledge that Starlink terminal is being used by a sanctioned or unauthorized party, we investigate the claim and take actions to deactivate the terminal if confirmed,” Starlink said in 2024.

But with tens of thousands of terminals in Ukraine alone, it could be a near impossible task to determine which terminals are authorised and which ones are not.