It felt like a watershed moment. During his state visit to Germany earlier this week, French President Emmanuel Macron called for Ukraine to be allowed to strike military targets within Russia with Western weapons. German Chancellor Olaf Scholz did not object and stressed that international law does allow for Ukraine to hit targets on Russian territory.

Prior to this, NATO Secretary-General Jens Stoltenberg had also expressed support, along with government representatives from the United Kingdom, Poland, and the Baltic countries. The United States and Germany so far had argued against it, citing fears of escalation.

Western weapons against Russian advance

In European capitals, Ukrainian President Volodymyr Zelenskyy has been increasingly pushing to break this taboo. His military appears to be getting weaker, partly because the United States has not delivered weapons for months. In northeastern Ukraine, near the Russian border, Russia is bombing Kharkiv, Ukraine's second-largest city, on a daily basis.

The Russian army has made several territorial gains and, according to Ukrainian reports, is gathering forces for a potentially larger push. So far, Ukraine has only attacked targets within internationally recognized Russian territory with its own weapons. Western weapons were only used against enemy troops on territories occupied by Russia on the Crimean Peninsula and in eastern Ukraine.

Colonel Lieutenant Yaroslav Matisek of the US Air Force and professor at the US Naval War College believes that Ukraine cannot defend cities like Kharkiv without using Western weapons against Russian targets beyond the Russian border. He told DW that allowing Russia to have a safe haven on its own territory was simply "a poor military strategy."

European instructors in Western Ukraine?

There are more taboos on the line. A presence of troops from several NATO countries in Ukraine is now no longer unthinkable. According to Colonel Oleksandr Syrskyi, commander-in-chief of the Ukrainian Armed Forces, he has signed papers regarding French military instructors. These could "arrive soon" to visit Ukrainian training centers, according to the general on social media on Monday. He spoke of an "ambitious project" and hopes that other partners would follow.

France initially toned down the message: They are in talks, according to media reports from Paris. Macron announced that he will present a plan next week to send instructors.

Sending troops for training to Ukraineis one possible scenario, French foreign policy expert Nicolas Tenzer told DW: "Probably France is ready to do that, I would say as early as possible." The could be sent to locations like Lviv or Kyiv.

If France actually sends instructors to Ukraine, it might not be alone. Poland and the Baltic states also do not rule it out. In February, Macron caused a stir when he was the first Western head of state who did not rule out sending troops to Ukraine. Until then, this was considered a firm red line — both for Moscow and the West.

At the beginning of May, Macron reaffirmed his position. If Russia succeeded in breaking through and Ukraine were to ask for Western troops to come to the rescue, they would have to think consider it, according to Macron. So far though, Zelenskyy has not made such a request.

Instructors to make up for shortage at front

"As Russia advances, NATO considers sending trainers into Ukraine," read a New York Times headline in mid-May. This would allow the government in Kyiv to train urgently needed, newly mobilized soldiers faster than before and to deploy them at the front, according to the newspaper. The main limitation seems to be: no direct combat between Western troops and Russian soldiers.

Matisek considers the dispatch of instructors easily feasible. "I think you can easily put a couple thousand Western forces into Lviv as part of a training contingent," says the military expert. The European Union has already conducted such a training mission within EU countries and could in future conduct such trainings in Ukraine, Matisek suggests.

He proposes to go even further: Western countries could station troops along the Ukrainian border and inside the country up to the bank of the largest Ukrainian river, the Dnipro, according to Matisek. "I think that it sends a very clear signal to Putin that the West is not going to tolerate further territorial conquest of Ukraine," explains Matisek. "If the Europeans would do that, that would probably free up at least 20 brigades of Ukrainian personnel to move a lot closer to the front."

Many political and defense experts oppose such ideas. Some accuse Macron and his supporters of exposing European dividing lines.

A limited no-fly zone?

If the West were to send troops to Ukraine, this would also mean "more air defense" to protect them, according to Matisek. In Germany, some politicians and experts even advocate that NATO countries shoot down Russian drones and missiles over Western Ukraine from their own territory.

At the beginning of May, members of parliament showed openness to this plan, according to a report by the Frankfurter Allgemeine Sonntagszeitung newspaper. Mentioned were Roderich Kiesewetter from the opposition CDU and representatives of the governing parties — Markus Faber from the FDP, Agnieszka Brugger and Anton Hofreiter from the Greens. The proposal itself comes from Nico Lange, an expert from the Munich Security Conference. Their aim is to protect the sky over Western Ukraine up to 70 kilometers (43 miles) deep, from installations in countries like Poland.

This would effectively be a limited no-fly zone. Chancellor Olaf Scholz is against any involvement of NATO and has criticized such ideas. Scholz has been lobbying for weeks for more deliveries of air defense systems to Ukraine. Berlin recently sent two more - a Patriot and an IRIS-T.

US expert Matisek understands the German restraint towards Russia due to historical reasons. However, he thinks the risk of escalation is acceptable. If the Western engagement remains limited and Russian missiles and drones are only shot down over Ukraine, not over Russia itself or its ally Belarus, then that would be a "near-humanitarian mission," according to Matisek.

Not everyone sees it this way. A limited no-fly zone would likely be particularly difficult to implement, say some observers in the West. So far, no head of state of a NATO country has spoken out in favor of it. Russia has threatened that Western soldiers in Ukraine would become targets of Russian attacks.

Moscow recently conducted troop exercises with tactical nuclear weapons. It justified the move by claiming that Western countries could send soldiers to Ukraine and allow Kyiv to attack Russian territory with their weapons.

This article was originally published in German.