The Ukrainian army's astute use of drones has been a cornerstone of its defence against the powerful Russian invader, but experts say their role is beginning to fade as heavy artillery takes over. In the early phase of the war, Ukraine's sky seemed filled with the remote-controlled aircraft deployed by President Volodymyr Zelensky's army to spy on the enemy, or go on the attack. During Moscow's early advance on Kyiv "it would have been extremely challenging for Ukraine to block (Russian President Vladimir) Putin's army without drones", said Paul Lushenko, a US Army Lieutenant Colonel and PhD student at Cornell University. "They could compound or exacerbate Putin's strategic and logistical challenges," he told AFP. The Turkish-made Bayraktar drone, known as TB-2, already famous worldwide, added to its stellar reputation during the defence of Ukraine's capital. On top of providing intelligence on Russian movements, drones also helped Ukraine offset much of its air force's weakness compared to that of Russia.