Editor's note: Rick Francona is a retired U.S. Air Force intelligence officer and CNN military analyst. The opinions expressed in this commentary are solely those of the author.
(CNN) -- CNN Pentagon Correspondent Barbara Starr reported Thursday that the U.S. intelligence community has information that Russian artillery is firing into eastern Ukraine. The artillery pieces shown in the released footage are Russian M-46 130mm field guns with a range of a little over 16 miles.
Why would the Russians do this? Simple -- this fits into their plan to support pro-Russian separatists in eastern Ukraine. The end game? I believe it is the eventual absorption of that region into the Russian Federation.
The area in red on the map is where much of the fighting between the Ukrainian government and the pro-Russian rebels has been occurring over the last month. The separatists have downed several Ukrainian military aircraft in this area as the fighting raged. It is also the area in which Malaysia Airlines Flight 17 was shot down in what most of us believe was a tragic case of mistaken identity and inept use of modern weaponry.
Over the past month, the Ukrainians have been successful in pushing the rebels into a pocket near the Russian border. One of the key weapons used by the Ukrainians is the Sukhoi Su-25 ground attack/close air support jet fighter. It is heavily armed and armored, meant to fly low and attack personnel and vehicles with a variety of weapons. Flying low makes it vulnerable to ground fire, however, especially shoulder-launched MANPADS, which are the heat-seeking surface-to-air missiles in the rebels' arsenal (also supplied by the Russians).
To address some of the vulnerability to ground fire, pilots can fly higher than the effective ranges of MANPADS.
Defending against these higher-flying aircraft requires a more advanced and capable air defense system -- like the SA-11 (called the "Buk" system by the Russians). From a variety of reports, it appears that the Russians provided a Buk transporter-erector-launcher-and-radar (TELAR) to the separatists. There is footage of an SA-11 TELAR being moved from this contested area toward the Russian border immediately after MH17 was shot down.
Just three days before, on June 14, the rebels shot down a Ukrainian military Antonov An-26 twin-turboprop cargo aircraft flying at an altitude of 21,000 feet. Since this altitude is significantly above the range of the MANPADS in either the Ukrainian or rebel arsenal, the obvious conclusion is that it was downed with a more capable system: the SA-11 system supplied by the Russians.
That event alone should have set off alarm bells in the civil aviation community. The downing of any aircraft operating at that altitude presented a different threat scenario than would an area in which shoulder-fired missiles were the only threat to aviation.
The subsequent -- and I believe mistaken -- downing of MH17 forced the rebels and their Russian sponsors to remove the SA-11 system from eastern Ukraine, although it is obvious to most observers what had happened.
Without the improved air defense umbrella provided by the SA-11, the separatists found themselves again subject to effective Ukrainian air strikes. On Wednesday, two Ukrainian Su-25 fighters were shot down while operating at an altitude of 17,000 feet -- just above the range of MANPADS, yet still at an altitude to deliver munitions with a degree of accuracy.
The Ukrainians believe the aircraft were downed with SA-11 missiles, but this time fired from inside Russian territory. The SA-11 has enough range to reach not only that altitude, but more than 20 miles into Ukrainian territory.
In a further development, on Thursday it appeared that the Russians had also begun fire support for the rebels, firing artillery from inside Russian territory into eastern Ukraine. While the M-46 130mm field gun seen in the photos can reach out to about 16 miles, the Russians have other systems that can reach as far as 25 miles or more.
This represents a significant change in the situation between Russia and Ukraine. Providing material support -- the money, weapons and training required to mount an effective insurgency -- to groups in foreign countries is a recognized method of assisting groups that are either carrying out your wishes or are furthering a foreign policy objective. We have done it routinely. Afghanistan is a prime example.
Firing artillery rounds into another sovereign nation with whom you are not at war is another matter entirely. This would be an act of war, yes, but it underscores just how seriously the Russians (read: President Vladimir Putin) view the survival of the pro-Russian rebels in Ukraine and their hopes that their continued fighting will achieve a key foreign policy objective.
Putin believes these rebels are his ticket to gradually acquiring eastern Ukraine without a Russian military invasion. This use of artillery in the midst of the international furor over the MH17 incident demonstrates his seriousness.
On Friday, the Ukrainians reportedly responded to the Russian artillery fire with mortar fire across the Russian border. This represents a significant escalation of the tensions along that border -- what was once an internal (albeit externally supported) conflict between Ukrainian nationals and pro-Russian separatists now has the trappings of a cross-border fight between two sovereign nations, one of which has immensely greater military power.
Both sides are calculating their next moves. From the Russian perspective, with its approximately 15,000 troops deployed along the border, this artillery fire is logical and almost obligatory support for ethnic Russians who they believe would rather be part of the Russian Federation.
From the Ukrainian perspective, this is Russian meddling in their internal affairs. Military action from the Russian side will draw a Ukrainian armed response. This is understandable, but the Ukrainians need to ensure that they are not playing into Vladimir Putin's game plan. At some point, the Russians may declare that they need to intervene to protect "Russian nationals in eastern Ukraine."
Sound far-fetched? Remember Crimea.