US sent Soviet-made air defense missile systems to Ukraine secretly acquired in the past.

According to information published by "The Wall Street Journal" on March 21, 2022, the United States sent Soviet-made air defense missile systems to Ukraine including 9K33 Osa NATO designation SA-8 Gecko that were secretly acquired by the U.S. in the past to study the technology of Russian military equipment.
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SA-8 Gecko air defense missile system of the Czech army. (Picture source Army Recognition)

The Ukrainian army is mainly equipped with military equipment acquired from Russia including air defense systems S-300V long-range surface-to-air missile systems, 9K35 Strela-10 NATO designation SA-13 Gopher, 9K33 Osa-AKM NATO designation SA-8 Gecko and 75 2K22 Tunguska SA-19 Grison anti-aircraft gun system.

Recently, the Ukrainian President Volodymyr Zelenskyy has requested the United States and NATO countries to provide more air defense systems to the Ukrainian armed forces to counter the air superiority of the Russian armed forces. Sending this type of Soviet-made military equipment will strengthen the air defense of Ukrainian territory and can easily be used by the Ukrainian armed forces who already know and use this type of equipment.

Army Recognition also reported on Sunday, march 20, 2022, that the United States is in talks with Slovakia and Bulgaria to provide Soviet-made S-300 air defense missile systems which are in service in these two countries to help Ukraine in the fight against the Russian army.

The 9K33 OSA NATO designation SA-8 Gecko is a Russian-made highly mobile, low-altitude, short-range tactical surface-to-air missile system that entered into service with the Russian army in 1971.

The SA-8 Gecko air defense missile system is based on a six-wheeled truck chassis designated BAZ-5937. SA-8 Gecko is armed with 6 missiles ready to fire, mounted on the roof of the vehicle. All versions of the 9K33 feature all-in-one 9A33 transporter-launcher and radar vehicles which can detect, track and engage aircraft independently or connected to an air defense system network.

The engagement range for the SA-8 Gecko missile is approximately 2–9 km and engagement altitudes of between 50–5000 m. The 9M33M2 "Osa-A" missile extends the ranges out to 1,500 - 10,000m and engagement altitudes to 25 – 5,000 m. The 9M33M3 missile greatly enhances the altitude engagement envelope to 10 – 12,000 m, and as such are also able to fly further (about 15 km/9 miles) but the system is not able to engage targets at longer ranges, due to other factors such as the radar tracking of the missiles.