WASHINGTON (AP) — About 100 Ukrainian troops will head to Oklahoma’s Fort Sill as soon as next week to begin training on the Patriot missile defense system, getting Kyiv closer to obtaining the long-sought protection against Russia’s missile attacks.

Ukraine for months requested that the U.S. provide the Patriot surface-to-air guided missile defense system because it can target aircraft, cruise missiles and shorter-range ballistic missiles. During his late December visit to the U.S., Ukrainian President Volodymyr Zelenskyy said the battery would make a significant difference in bolstering Kyiv’s defenses against Russia’s invasion.

The number of Ukrainians coming to Fort Sill is approximately the number it takes to operate one battery, and they will focus on learning to operate and also maintain the Patriot, Pentagon spokesman Air Force Gen. Pat Ryder said Tuesday.

Kyiv’s decision to take troops off the battlefield to train across the Atlantic in the U.S. is unusual, although Ukraine has sent forces for short-term training at European bases for other complex systems it has received, such as on the longer-range High Mobility Artillery Rocket System.

Patriot training normally can take several months, but, “The longer those troops are off the line, they’re not actually engaged in combat,” Ryder said, so the training will be shortened.

Fort Sill was selected because it already runs Patriot training schools, Ryder said.

The U.S. pledged one Patriot battery in December as part of one of several large military assistance packages it has provided Ukraine in recent weeks. Last week Germany pledged an additional Patriot battery.

Each Patriot battery consists of a truck-mounted launching system with eight launchers that can hold up to four missile interceptors each, a ground radar, a control station and a generator. The Army said it currently has 16 Patriot battalions.

The Patriot batteries will complement a variety of air defense systems that both the U.S. and NATO partners have pledged to Ukraine, as it faces an evolving barrage of missiles and drones against its civilian population and infrastructure from Russia in the nearly 11-month-old conflict. In the last few months Germany has pledged four IRIS-T air defense systems; the U.S. has also pledged eight mid-range National Advanced Surface-to-Air Missile Systems, or NASAMS, and Avenger air defense systems.

The training at Fort Sill was first reported by CNN.