In May of last year, I came across these missile cases in a small village called Novyi Bykiv.

They were sitting outside a rec center in an area that had been liberated by Ukrainian forces just weeks before.

You can see on the case how it starts with the serial number 9M317... the 9M317 is a missile used for what is called the Buk missile system.

... the same system that shot down MH17 in eastern Ukraine back in 2014, killing hundreds of civilians.

So we need to back up and provide some context here:

On a summer day in 2014, a civilian commercial flight was traveling from Amsterdam to Kuala Lampur.

A Russian unit supplied the missile system that shot down the plane in Eastern Ukraine.

All 298 passengers/crew died.

Having departed from Amsterdam, it was, as one Dutch person told me, The Netherland's version of 9/11.

The Joint Investigation Team led by the Dutch concluded that the Russian unit that supplied the missile system was known as the 53rd Anti-Aircraft Missile Brigade.

It was this unit that we were trying to find.

Were they fighting again in Ukraine this past year? No one knew.

Like so many leads, our original lead in Novyi Bykiv was a dead end. The 53rd hadn't been there.

But the question remained: where had the 53rd been? Had they been active somewhere in Ukraine?

Over the past year we cultivated intelligence, law enforcement, military sources everywhere: the U.S., Ukraine, Poland, France, + the Netherlands.

We heard vaguely that the 53rd had been in the Kharkiv region.