Kyiv, Ukraine – Denys, a soldier living in Kyiv on leave from Ukraine's eastern front, is outraged at how long it takes for each shipment of Western weapons to reach the country.

“There is always a no first: no tanks. No missiles. No fighter jets,” he told Al Jazeera, repeatedly pointing out that Western allies had either refused to supply Ukraine with certain types of weapons or had strictly regulated their use. Denys withheld his last name and the location of his military unit in accordance with the rules of war.

“And every no costs lives. Not just ours. We are big boys, we have seen a little bit of life, but that of children, of small children who were burned alive or torn to pieces…” said the 27-year-old, close to screaming, as he stood between a flowering linden tree and an ice cream stand in central Kiev. “And then comes a 'maybe, maybe', and it goes on like that for months, and then comes a 'yes', but it is always too late.”

Ultimately, the Western states agreed to supply tanks, missiles and fighter planes – but after painfully long discussions that cost human lives, he said.

The recent “yes” by the United States and nearly a dozen Western states following Russia's recent push and relentless bombing of Kharkiv, Ukraine's second-largest city, gives them permission to use the modern weapons they have supplied – or will soon supply – to launch attacks inside Russia.

Washington and its allies fear angering Russia, whose President Vladimir Putin has repeatedly indicated that the use of nuclear weapons is under discussion if Ukraine or the West cross another “red line,” such as shelling Crimea or Putin's pet project, a bridge connecting Crimea to the Russian mainland.

But Ukraine has already crossed many military and political lines, including expelling Russian troops from occupied territories and launching drone attacks on airfields, military bases, ports and oil depots deep inside Russia. These acts have infuriated Moscow, but not enough to require it to use nuclear weapons.

The latest Western “yes,” which came on Thursday and followed months of requests from Kyiv, is more of a “yes, but.”

The White House said Kyiv could begin using US weapons for “limited attacks” inside Russia – but only in the areas bordering the northeastern Kharkiv region.

In early 2022, Russian forces captured the region and its administrative capital of the same name, but were expelled months later following a maneuver orchestrated by current Ukrainian top general Oleksandr Syrskii.

Moscow resumed his attempts to take Kharkiv In early May, they captured several border villages near the western Russian region of Belgorod. The presence of artillery in the area allowed troops to advance on Ukrainian targets and then retreat to Russian soil, where they knew they were safe from Ukrainian defense forces.

The White House's latest “yes, but” refers to air defense systems, artillery and guided missiles. However, a ban on attacks with long-range missiles remains in place.

Other Western weapons that can now be used against Russia include 24 Dutch F-16 fighter jets equipped with long-range missiles, as well as Soviet-era jets supplied by Poland, Slovenia, Slovakia and North Macedonia – countries that have also given their approval in recent days.

The Ukrainian pilots will soon complete their months of training to fly F-16 aircraft and could fly their first missions within a few weeks. Until now, their missions had to be limited to Ukrainian airspace. Not anymore.

The jets – along with a handful of Soviet aircraft from Ukraine – can fire French-made air-launched cruise missiles, so-called SCALP-EG missiles (Systeme de Croisiere Autonome a Longue Portee).

Britain has not yet given permission to deploy the SCALP's almost identical twin Storm Shadow missile, but has previously approved the deployment of its combat drones on Russian soil. Turkey has also allowed Ukraine to deploy its Bayraktar drones there.

The United States, Great Britain, Germany and Norway have already supplied Ukraine with ground-based launchers for HIMARS and ATACMS missiles, which have initially proven effective in attacks on the annexed Crimea and occupied Ukrainian territories.

But in recent weeks Russia has begun deploying advanced electronic jamming systems to render these satellite-guided missiles – as well as the GPS-guided Excalibur artillery shells – ineffective.

“She [Russians] “We have made great progress,” said Lieutenant General Ihor Romanenko, the former deputy chief of the General Staff of the Ukrainian Armed Forces. “We are taking this seriously. We need to develop our own means to suppress their electronic jamming and create our own jamming systems,” he told Al Jazeera.

But the West’s permission is unlikely to bring about a change.

“The tables will not be turned. The coming months will be about containing Russia,” Kyiv-based analyst Igar Tyshkevych told Al Jazeera.

The permission is a result of Western attempts to “find compromises with Russia,” he said. “That is slowly changing because Russia is showing its true face – an empire that is trying to pursue politics according to the patterns of the 19th century.”

The decision was a result of the “sustained, barbaric bombing” of Kharkiv and other border towns, as well as Russia's plans to launch an offensive in northern Ukraine at the wooded junction of the Kharkiv and Sumy oblasts, said Nikolay Mitrokhin, a researcher at the University of Bremen.

The offensive against Kharkiv could begin within weeks of the deployment of tens of thousands of newly drafted and trained Russian soldiers.

“The Ukrainian armed forces do not have enough resources to secure the border and will have to strike from the forests quite far from the border,” Mitrokhin told Al Jazeera.

Ukraine is suffering from a severe shortage of new soldiers. President Volodymyr Zelensky's government delayed mobilization for months, fearing a public outcry, and has not allowed the demobilization of experienced, battle-weary veterans. The troop shortage coincided with a shortage of weapons and ammunition following months of delays in Western deliveries.

In recent weeks, teams of conscripts and police have arrested thousands of men in public places, from subway stations to traffic jams.

“There is hope that Ukraine will succeed in destroying Russian columns in the marching phase and artillery with multiple rocket launchers in the deployment phase,” Mitrokhin said.