WASHINGTON (AP) — As the war in Ukraine evolves, so do the needs of the Ukraine military. That's the case U.S. officials are making as they explain the decision to a include a mobile rocket-launching system to help the Ukrainians fight the Russian assault in the country's east.

In the initial phase of the invasion, Ukraine relied on anti-tank and anti-armor weapons to repel what many thought would be a quick assault on Russia's smaller neighbor. But it's now turned into a grinding artillery battle that could go on for months and will require different types of weapons systems. A look at what's in the latest $700 million in U.S. military aid:

HIMARS

It stands for High Mobility Artillery Rocket Systems. It's basically a rocket-launcher on wheels and gives troops the capability to strike a target and then quickly move away. It's ideal for striking artillery positions. Each HIMARS has a pod that can carry six precision guided rockets. The type the U.S. is providing has a range of about 40 miles and will be useful as Ukraine tries to push back Russian forces making gains in the eastern Donbas region of the country. Colin Kahl, undersecretary of defense for policy, told reporters that Ukraine will initially receive four of the HIMARS systems, which can be deployed after about three weeks of training, and an unspecified number of rockets.

RADAR

Also in the package are five counter-artillery radar systems and two air-surveillance radar systems. These are in addition to counter-artillery radar already sent. The goal is to track incoming fire so the Ukrainians can take it out, aided by the artillery sent by the U.S., Britain and other European allies.

ANTI-TANK WEAPONS

Though the nature of the fight has shifted, Ukrainian forces are still trying to take out Russian tanks and other armored vehicles. That means they will need more of the Javelin anti-tank missiles that played such a major role in repelling the initial invasion in February. This latest package includes 2,000 more Javelins.

ADDITIONAL

The U.S. is also sending artillery rounds for the 155mm howitzers it has provided to Ukraine for its defense; four Mi-17 helicopters; and other equipment. The U.S. has now committed about $5.3 billion in security assistance to Ukraine since the beginning of the Biden administration, including about $4.6 billion since the Feb. 24 invasion. More is on the way: Congress last month approved $40 billion in aid to the country.