A 90-truck aid convoy crossed the border into Ukraine from Russia on Friday without "clearance or participation of the International Red Cross" or Ukrainian agreement as previously negotiated.

Sound like small beer? Consider the immediate statement by Ukrainian state security chief Valentyn Nalivaychenko (via Reuters): "We consider this a direct invasion by Russia of Ukraine."

The Russian Foreign Ministry issued its own statement saying that it was tired of waiting for Ukrainian officials to approve the delivery of humanitarian aid, which had been stalled for weeks amid the violence in eastern Ukraine. From their statement:

“All the excuses to delay the delivery of aid to people in the area of a humanitarian catastrophe are exhausted. The Russian side has made a decision to act. Our column with humanitarian cargo starts moving toward Luhansk.”

According to the New York Times, the Red Cross opted out of participating due to the “volatile security situation,” which included the overnight shelling of Luhansk, one of the urban centers currently encircled by Ukrainian forces aiming to stamp out the pro-Russian insurgency.

Here's how Sweden's foreign minister saw the movements:

So what's exactly the big deal here? Well, as Andrew Roth and David Herszenhorn noted, there are plenty of ulterior motives for the introduction of massive white trucks into the battlefield. Among them:

Spreading the conspicuously large white aid trucks throughout the embattled city could effectively impose a cease-fire, essentially daring the Ukrainians to fire at vehicles that have been sent to provide desperately needed humanitarian assistance.

In essence, affording the rebels some time as they barely cling onto Luhansk, one of their final strongholds, could allow them to regroup just as Ukrainian forces seem close to defeating them.

The Economist writing about the trucks, which first arrived on the border just over a week ago, characterized their potential to frustrate Ukraine's counteroffensive against the rebels:

But if many cross into Ukraine, they are unlikely to leave, becoming a beachhead for a long-term Russian presence that turns the war into a frozen conflict, which would suit Mr Putin fine. For Mr Putin, Ukraine needs to stay fractured and destabilised: just how this happens is less important."

Of the 300 trucks, just under a one-third of them were said to have entered Ukraine on Friday. For the time being, that leaves another 200 waiting to be dispatched.

Ukrainian officials quickly announced that they would not fire upon the aid trucks. State security chief Valentyn Nalivaychenko added:

Ukraine will liaise with the International Committee of the Red Cross so that we, Ukraine, are not involved in (accusations of) provocations that we have been holding up or using force against the vehicles of so-called aid." 

He said that while airstrikes against the convoys have been ruled out, airstrikes against the rebels are fair game.