Starting Thursday, Ukraine's Defense Minister Oleksii Reznikov hailed the arrival of the longest-range missiles the United States has provided thus far in the four-month long war.

"HIMARS have arrived to Ukraine. Thank you to my colleague and friend SecDef Lloyd J. Austin III for these powerful tools! Summer will be hot for Russian occupiers. And the last one for some of them,"  Reznikov announced on Twitter.

The HIMARS, or High Mobility Artillery Rocket Systems, were announced as part of the latest $700 million weapons package to Ukraine on June 1. In total four of the systems will be transferred as part of the authorization, with the possibility of more in coming aid packages.