(CNN) Russia has relied far more heavily on less sophisticated, so-called "dumb" bombs than it has on its arsenal of precision-guided munitions in its punishing war on Ukraine. It's a dynamic that US officials are watching closely for clues about the state of Russia's military — as these indiscriminate weapons kill scores of civilians.
Russia has used a combination of missiles, artillery and rocket launchers to pummel major Ukrainian cities over the past two weeks, Lt. Gen. Scott Berrier, the head of the Defense Intelligence Agency, told the Senate Intelligence Committee on Thursday. On Friday, Russia launched a barrage of missile attacks on a wide range of targets across central and western Ukraine, causing substantial damage and using what Russia's defense ministry said were "high-precision long-range weapons."
But the number of "precision-guided munitions that are being dropped from aircraft ... is small," Berrier said.
US and Western officials say they don't know why Russia hasn't used more of these more sophisticated weapons, which its Su-34 fighter-bomber fleet regularly employed, along with other unguided bombs in Syria. It's an approach some US military and intelligence officials say could signal another surprising weakness in Russia's military campaign — or simply a terrifying willingness to employ brutal tactics that lead to countless civilian deaths in a war that many officials think could last weeks or even months.
"It's hard to say at this point whether that's driven by expense, if that's driven by a lack of inventory or if that's just driven by a desire to be more brutal in the use of force," a senior NATO official said on Thursday, calling it a "big question."
Precision-guided munitions, or PGMs, are more expensive, time-consuming and complex to produce than unguided munitions and there has long been speculation that Russia's stockpile is relatively limited. It is possible, some outside analysts say, that Russia is simply holding its PGMs in reserve for later in the conflict — or as an emergency precaution in case Russia finds itself in conflict with NATO. One source familiar with the intelligence said that the Russia burned through the proportion of its PGM arsenal that it allocated for the operation in the early days of the conflict, when Moscow enforced stricter rules of engagement that eschewed widespread civilian casualties.
But whatever the reason, officials say the impact is now being borne by Ukrainian hospitals, schools and apartment buildings destroyed by Russia's indiscriminate bombing campaign — even as a senior defense official cautioned on Wednesday that the US cannot prove whether guided or unguided munitions were used against a given target after the fact.
The strategy may also create direct costs for Russia, according to one senior military official familiar with the latest intelligence. This person said that the use of some of Russia's "dumb" bombs requires its pilots to fly lower, making them more vulnerable to Ukraine's surprisingly effective anti-air defenses. Over the past several days, officials have noted a sharp decrease in overall Russian air activity over Ukraine.
As the war enters its third week, Russian forces have been bogged down by not only a stiff Ukrainian resistance but myriad logistical and resupply missteps that Western officials have increasingly said show fundamental weaknesses in Russian planning and readiness. CIA Director Bill Burns on Tuesday said that Russian President Vladimir Putin launched the invasion in part based on the assumption that his military was capable of a quick and decisive victory at minimal cost — one of several assumptions that Burns said had "been proven wrong."
"It is possible that we know more about the true state of fighting and the Russian readiness and capability at this point than Putin does himself," the senior NATO official said.
Officials say there is still no question that Russia's military is vastly superior to Ukraine's fighting force and that Ukraine's prospects remain grim. Even in the face of Ukrainian resistance, Russia has made steady progress across the country. But intelligence officials have stopped predicting the imminent fall of Kyiv as the conflict has settled into a grinding war of attrition. The senior NATO official said he now believes the war may be measured in "months to years," rather than days or weeks as Western officials has initially assessed.
Director of National Intelligence Avril Haines said on Thursday that the US intelligence community had been caught by surprise by the clumsy execution of Putin's military strategy.
"We did well" predicting that Putin had underestimated the resistance he would face in Ukraine, she said. "We did not do as well in terms of predicting the military challenges that he has encountered with his own military."
US and Western officials say that it's difficult for them to nail down Russian losses, both in terms of battlefield casualties and destroyed equipment. Ukraine has reported that around 12,000 Russian soldiers have been captured or killed and more than 100 aircraft and helicopters, 317 tanks and over 1,000 armored personnel carriers have been eliminated.
But even if those numbers can't be confirmed, officials say, it's clear that Russia has suffered significant troop and equipment losses.
"When you look at just the trash that is coming in from Russia on these train cars now, in terms of trucks and these little cars — they've got like civilian trucks and cars now on trains coming in to try to replace some of these heavier trucks that have been lost to Ukrainian counterattacks — that's amazing," said the senior NATO official.
Russia's defense ministry on Wednesday also acknowledged that some conscripts were taking part in the war, while US officials say that Moscow is also seeking to recruit foreign fighters from Syria. Other foreign fighters, from Chechnya, are already in Ukraine, as is the mercenary group Liga, formerly known as the Wagner Group.
Western officials see those supplementary forces as a potential sign that Russia is struggling to assemble sufficient combat power to continue its assault.
"We find that noteworthy that [Putin] believes that he needs to rely on foreign fighters to supplement what is a very significant commitment of combat power inside Ukraine as it is," a senior defense official told reporters on Thursday.
Russia has also struggled to effectively supply its forward-deployed combat formations in the field with fuel, food and weapons. Russian forward-deployed units have often sprinted out ahead of their logistics train, leaving the support units vulnerable to Ukrainian counterattack.
Meanwhile, a 40-mile convoy of Russian combat and logistics vehicles was stalled for days north of Kyiv, in part thanks to mechanical breakdowns and congestion and in part thanks to Ukrainian efforts to stymie its progress. However, by Thursday the convoy had "largely dispersed and redeployed," according to Maxar Technologies satellite imagery.
Still, despite Russian missteps, despite what officials have described as a heroic Ukrainian resistance, Western intelligence services are not assessing that Ukraine has turned the tide of the invasion. Russia's military remains qualitatively and quantitatively superior. Putin continues to carry out a sustained bombardment of Ukrainian cities with indiscriminate "dumb" bombs — including against civilian infrastructure — even in the face of international condemnation. Officials now believe that he is preparing to attempt to cut off food, water and potentially power supplies to Kyiv, as he has in other major cities within Ukraine.
"We see no signs that Putin has deviated from what his strategic political objectives are, nor do we see any signs that the military end states have changed," said the senior NATO official. "The only major difference, aside from the miserable challenges that they're facing, is that they've just become more violent — not just against the military but against civilians."