On May 23 the former Commander in Chief of the Ukrainian army had a pessimistic assessment of the war in Ukraine (machine translation):

Former commander-in-Chief of the Armed Forces of Ukraine, and now Ambassador to the UK Valery Zaluzhny said that Russia has overtaken Ukraine in innovations on the battlefield.
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According to him, Ukraine at the moment "does not manage to continuously generate and scale innovations, even in those areas where yesterday we were ahead of the enemy."

"The enemy has already overtaken us and we are lagging behind – and we must be honest about this," he said.
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The ex-commander-in-chief believes that the Russian Federation is now waging a war of attrition. In response, it is necessary, according to Zaluzhny, "to undermine the economy and social component in order to deprive Russia of the possibility of scientific and technological development and start the processes of civil unrest and disintegration."

How to do this, the ex-commander-in-chief does not specify, …

Zaluzhny was likely not only referring to the drone war which Russia is winning but also to the mediocre state of Ukraine's air defenses.

A day after Zaluzhny, the spokesman of the Air Force of Ukraine confirmed his take (machine translation):

Russia has improved its ballistic missiles, so Patriot systems have become worse at shooting them down. This was stated by the head of the Communications Department of the Air Forces of the Armed Forces of Ukraine Yuriy Ignat, commenting on today's night shelling of Kiev.

Iskander-M missiles, which attack along a ballistic trajectory, have been significantly improved and upgraded

"We are talking about shooting radar traps, which each missile can shoot during the approach to the target. Another is the flight of a ballistic missile along a quasi-ballistic trajectory, when the missile does not fly in a straight line, but already performs maneuvers, " he said on the telethon.

The new Iskander versions use decoys to confuse the air defense radars. They also maneuver during the last phase of their flight making their interception nearly impossible.

Reporting on the large scale Saturday night attack on Ukraine the Washington Post noted that the U.S. provided Patriot air defenses systems in Ukraine had failed (archived):

The Russian assault involved nearly 400 missiles and drones, including nine ballistic missiles that Ukrainian air defenses, already strained and in short supply, failed to intercept, Ukraine’s air force said.

Some of the Russian missiles destroyed at least one Patriot air defense battery. Each battery consists of a radar, a combat control station and two or more launcher vehicles. The cost for a full battery is about $1 billion. Each fired missile comes at a price of $2-4 million.

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The Patriot battery killed during the weekend strike was not the first one to meet that fate.

The Military Watch Magazine has documented the history of the system in Ukraine:

The Iskander system was first confirmed to have successfully destroyed a Patriot system on February 23, 2024, with a subsequent strike destroying another system near the Sergeevka locality on March 10 that year, leaving ground forces in the region exposed. Subsequently in the second week of July, 2024, new footage confirmed the destruction of two batteries in the Odessa region, while on August 11 three more missile batteries and an AN/MPQ-65 radar were reported to have been destroyed in Iskander-M strikes. One of the Iskander-M’s more recent successes saw the destruction of the Patriot’s AN/MPQ-65 multifunctional radar station, combat control cabin, and missile launch vehicles all destroyed in the Dnepropetrovsk region.

Together with the one on Saturday/Sunday that sums up to a total of ten destroyed systems. That is likely more than half of the total provided by the U.S. and its allies.

The Patriot air defense system is quite old. The first version was used 35 years ago during the first U.S. war on Iraq. It largely failed to achieve its mission:

In 1992 a military report titled ‘Patriot Missile System Effectiveness During Desert Storm’ found that of the 158 missiles fired during the Gulf War, 45 percent were launched against false targets. An early 1990s study by Theodore Postol, professor of Science, Technology and International Security at the Massachusetts Institute of Technology and prominent expert on missile technologies, highlighted: “The Patriot's intercept rate during the Gulf War was very low. The evidence from these preliminary studies indicates that Patriot's intercept rate could be much lower than 10 percent, possibly even zero." Even “the most primitive of adversaries" could easily evade interception, his study concluded.

New versions of the Patriot's radar and missiles, PAC-2 and PAC-3, were introduced but continued to fail:

Following the revelations of the Patriot system’s shortcomings in the Gulf War, there were considerable hopes in the Western world that its modernisation would allow it to provide a much more viable defence against ballistic missile attacks. Such hopes were disappointed by its performance during the 2003 invasion of Iraq, and moreso 14 years later when further modernised variants failed to intercept a strike by makeshift ballistic missiles launched by Yemeni paramilitaries against Saudi Arabia in 2017. The Yemeni missiles were shown by satellite imagery and by photos and videos of the attack not to have been neutralised, despite claims by the Saudi and U.S. government sources to the contrary. Analysis conducted by a research team of missile experts showed a warhead flying unimpeded over Saudi Arabia despite its large arsenal of modernised Patriot batteries protecting the affected area.

The magazine concludes:

The questions more recently raised by Ukrainian officials regarding the Patriot system’s reliability against Russian ballistic missile attacks thus fit in with a long history of underwhelming performances in such a role. This has significant implications for militaries across the Western world and in Northeast Asia that rely on the system for their defence.

Another failure point of the Patriot system is the notorious lack of ammunition needed for it. According to The Economist (archived) the current production rate for Patriot systems is 650 missiles per year. Over the same time frame Russia is producing 750 ballistic missiles each at about 10% of the price of one Patriot missile.

Despite the poor record of the system Ukraine is, according to the Washington Post, still eager to acquire more of them (archived):

KYIV — Ukraine is increasingly worried about securing more U.S.-made Patriot air defense systems, as stockpiles sent during the Biden administration are drying up and the new administration is resistant to sending more, according to six Ukrainian and Western officials.
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Ukraine’s dire need for Patriots was apparent over Memorial Day weekend when its air defense forces failed to intercept any of the nine ballistic missiles launched Saturday night and early on Sunday. Two of the missiles were directed at Kyiv, according to Ukraine’s air defense forces, where at least two Patriot units are believed to be stationed.

One of those Patriot units most likely no longer exists.

The Post fails to explain why Ukraine should or would ask for more Patriot systems when, as the same report says, these fail their purpose.

The Post's opinion editors are even worse. Despite multiple reports in their own paper that Patriot systems are not able to defend against Russian missiles they falsely state (archived) that they can do so, only to then repeat that they don't:

What scares Ukraine more than the drones, however, is its diminishing stockpile of U.S.-made Patriot air defense systems. Ballistic missiles fired by Russia can be reliably countered only with Patriot launchers. On Saturday night, Ukraine failed to intercept nine such missile launches.

The editors seem to imply that Ukraine failed to intercept the Iskander missiles because it was lacking Patriot air defense missiles. But that was not the case. Video from the Saturday night attack shows the firing of at least 14 Patriot missiles by two batteries before one of them goes up in flames.

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None of the 14 fired air defense missiles had hit the incoming ballistic missile.

[The Post editors are lobbying for secondary sanctions in form of additional tariffs on products from anyone who buys basic materials from Russia. The tariffs would have to be paid by U.S. consumers. They would hurt the U.S. more than they would hurt Russia and certainly fail to help Ukraine.]

To summarize: Patriot air defenses are a chimera. The system has failed its purpose, to reliably defend against ballistic missile, since its creation.

The only reliable target it manages to intercept each and every time a missile is launched is taxpayer money. One wonders how many bribes are flowing to generate further requests for it.