Ukraineās counteroffensive began two months ago, but in many ways its forces have been preparing for it for years by learning how to fight like NATO militaries, with a mix of infantry, artillery, armored vehicles and air power.
But the Biden administration waited more than a year before letting NATO countries send F-16 fighter jets to Ukraine. By the time pilots are trained on the advanced aircraft, it will be too late for them to assist and protect ground forces slogging through this phase of fighting.
All of which has raised a question: Without significant air power ā a pillar of the warfare tactics that the West has urged Ukraine to adopt ā can the counteroffensive prevail?
The answer appears to be yes, as current and former officials in Ukraine, the United States and Europe, as well as Western defense analysts, said in interviews last week as the counteroffensive ground on, with volleys of artillery fire and drone strikes but no major breakthroughs.
But it is likely to be far more difficult without the jets.
āIt will have to happen without the F-16,ā said Philip M. Breedlove, a retired United States Air Force general and former NATO commander, ābut I believe they can.ā
A former F-16 pilot, Mr. Breedlove said there was āgreat benefitā for Ukraineās forces to learn and deploy the so-called combined arms tactics that are the backbone of modern ground warfare, given that they āare going to be applicable in many different phases of what you do, no matter what.ā
Nevertheless, he added, āIf you expect Ukraine to fight like we fight, then they have to have the tools that we have, and we have not given them those tools.ā
Gen. Valery Zaluzhny, the top Ukrainian commander, has made the same point with considerable frustration.
Some experts said the dearth of air power had put Ukraine at a disadvantage this summer against Russian attack helicopters that have picked off Ukrainian tanks and armored vehicles. At least some of the helicopters are equipped with anti-tank missiles that are shot either too far or too low to be intercepted by Ukraineās air defenses, according to Britainās Defense Ministry.
Col. Markus Reisner, who oversees force development at Austriaās main military training academy, said that with more warplanes, Ukraine could better defend its ground troops from those attacks.
āThis is what it is actually intended for,ā said Colonel Reisner, a trained intelligence officer. āMilitary logic tells you, you have to have air superiority to conduct successful land operations.ā
He added: āSome American generals, they say, āWell, itās not what the Ukrainians need at the moment.ā I think this is a political statement, itās not a military logical statement.ā
Neither Ukraine nor Russia ā despite its seemingly overwhelming advantage ā has managed to achieve air superiority since the war began in February 2022.
Back then, Russia had 10 times as many fighter aircraft as Ukraine ā 772 to 69 ā including some that were far more technologically advanced, according to the Global Firepower Index, which ranks conventional war-making capabilities. Yet in the 18 months since, both sides have relied on artillery, drones and long-range missiles to attack.
That is because both Ukraine, with Patriot missiles, among other weapons, and Russia with its S-400 air defense systems, have formidable air defenses that have largely deterred each other from launching airstrikes near or behind the front lines with piloted warplanes.
For the most part, Ukrainian pilots currently flying their Soviet-era MiG and Sukhoi fighter jets take care not to get too close to their targets or to stay in the air for too long, to avoid becoming targets themselves. They get as close as they dare and then fire missiles, including long-range missiles recently provided by Britain and France, at fuel and ammunition depots and other military targets before darting away.
In view of those limitations, a Biden administration official said in an interview last week that it was unclear whether Ukraineās forces would be able to provide support to ground troops even if they had the F-16s. The official spoke on the condition of anonymity to discuss an issue that has become a sore point to the Ukrainians.
After Ukraine suffered heavy losses early in the counteroffensive by trying to follow the combined-arms approach, some commanders decided to abandon the effort and return to the tactics they know best ā firing artillery and missiles to degrade Russiaās fighting capability in a war of attrition.
That was not a complete surprise to military experts, who said the problems went well beyond the absence of air power. Retired Col. Steve Boylan, a trained U.S. Army aviator and a former spokesman for the Armyās Combined Arms Center in Fort Leavenworth, Kan., said it had taken years for American forces to learn āhow to do it effectively ā and not in the middle of a fight.ā
As its name suggests, the modern fighting method combines infantry troops, armored tanks, artillery ground fire and air power in an effort to dominate all the domains of ground warfare. Mr. Boylan said the tactics were developed as a better way to fight after the bloody trench warfare of World War I, but it was not until the 1990-91 Persian Gulf war that American troops fought in the combined arms units as they are deployed today.
Fighting without one of the elements ā like air power, in Ukraineās case ā may force units to adjust, but āI would suspect that they would take our instruction, training and tactics as a baseline and modify it to what works best for them,ā Mr. Boylan said.
Yet for all that air power can bring to a battle, he said, āuntil you get troops on the ground, and actually take it, you donāt own it. And you canāt hold it.ā
As it is, Mr. Breedlove said, Ukraineās military is already one of the best-equipped and most battle-tested in Europe. Last week, President Volodymyr Zelensky of Ukraine said that plans for obtaining Western warplanes were moving forward, adding, āI have no doubt that F-16s will be in our skies.ā
But that will require a lengthy training period, beginning for many with language lessons. American officials have said that Ukraine has identified only eight combat pilots ā less than a single squadron ā who speak English well enough to start at least a year of training. About 20 others are being sent to Britain this month to learn English.
Sending just a handful of F-16s into battle would not make much difference in the war, said Douglas Barrie, a military aerospace expert at the International Institute for Strategic Studies in London. āItās got to be adequate, itās got to be up to the task,ā he said.
If Ukraine had multiple properly trained and equipped squadrons of F-16s, Mr. Barrie said, āwould it have helped in the counteroffensive? Itās a theoretical question, but the theoretical answer is yes.ā
He said that Ukraineās forces āwere never going to be in a positionā to launch a Western-style combined-arms offensive without air power.
Then again, he added, āIf they hadnāt had any of this training, would we now be trying to figure out how to get the Russians out of Kyiv?ā
Eric Schmitt contributed reporting from Washington.