For months, Ukrainian President Volodymyr Zelenskyy warned that come winter, there would be even heavier Russian attacks from the air.

In the late fall, Russia started launching increasing numbers of drones, before December 29 saw the biggest attack since Moscow's full-scale invasion began almost two years ago. More than 100 different missiles and huge swarms of drones were sent over Ukraine, with some 30 people killed in the capital, Kyiv, alone.

With some 700 drones launched, December was a record month. Russia targeted not just Kyiv, but the large cities of Kharkiv, Dnipro, Odesa, Kherson and Lviv as well.

Shortly before the New Year, Ukraine attacked the Russian Black Sea Fleet in Russian-annexed Crimea, hitting a landing ship. Sites in the southern Russian city of Belgorod, located near the Ukrainian border, also came under attack multiple times, with Russian authorities putting the death toll at more than two dozen.

It cannot be said for certain whether the Russian attack at the end of December was a kind of retaliation, but what is certain is that Russia has a clear edge over Ukraine with its aerial attacks, as it simply possesses more weapons. There were more attacks in the first days of January.

Ten seconds to hit a drone

Ukraine has to protect not only its troops on a front measuring more than 1,000 km (621 miles) but also military and civilian objects deep within the country. This forces it to conserve its resources: The most expensive Western air defense systems are employed mostly against Russian missiles in the heart of the country. The cheaper Iranian Shahed 136 drones are hunted down, among other things, by the self-propelled Gepard anti-aircraft guns supplied by Germany.

So-called mobile groups — mostly Ukrainian soldiers on pick-up trucks armed with portable air defense systems or even just machine-guns — are also in operation. "When a Shahed flies past, a mobile group has 10 seconds to locate it and hit it with a shoulder-fired surface-to-air missile," Yurii Ihnat, the spokesman for the Ukrainian air force, told DW.

As is the case with other weapons, Ukraine has a mixture of former Soviet and Western air defense systems, including US Patriots and German IRIS-Ts. According to official figures, Kyiv has three batteries of each of these weapons, with more said to be on their way.

Great reliance on West

Ukraine has a strong air defense thanks to help from the West. But that is also its big weak point, as all systems have one thing in common: The missiles they require are hard to obtain. Even Soviet ammunition is procured in the West from countries like Bulgaria and Slovakia, Ihnat says.

"We don't produce any ammunition for air defense these days. We need large quantities to shoot down missiles and drones," he says.

Another problem is that modern Western missiles, like those for the Patriot system, for example, are complex and slow to produce. In addition, there is barely any assistance coming from the US at the moment because Republicans are blocking a new aid package worth billions. The Ukrainian armed forces are trying to make progress with their own developments, but that takes time.

It is a secret how many air defense missiles Ukraine still has at its disposal to ward off new Russian attacks. Recent deployments give no reason to think that Ukraine is rationing them, Ukrainian military expert Oleksandr Musiienko told DW, adding, however, that there was a need for more.

Mobile groups had just enough ammunition "to stand up to the next heavy attacks," Ukrainian General Serhiy Nayev told French news agency AFP on Wednesday, warning that more supplies would be needed in the middle to long term.

More big attacks to come, say experts

Ukraine's forces are currently shooting down about 85% of Russian missiles and drones, according to a recent assessment by the commander of the Ukrainian air force, Mykola Oleshchuk.

Western experts such as Gustav Gressel from the think tank European Council on Foreign Relations (ECFR) highlight differences according to the type of attack, with the success rate higher in the case of attacks by single missiles or drones and lower — about 70% — in the case of massive ones.

Gressel told DW it seemed as if Moscow had wanted to save up its particularly expensive missiles in the summer and fall months, deploying them more rarely. According to estimates by Ukrainian intelligence services, he said, Russia can produce a total of some 100 missiles of various types per month but that this number could rise. Russia is also stepping up its drone production.

There is nothing to suggest that aerial attacks on Ukraine will become less frequent. Military analyst Musiienko believes that up to three more massive attacks on the scale of the recent ones are imminent.

This article was adapted from German.