One morning at the end of February, the Ukrainian power grid was disconnected from the larger Russian electrical grid that the country had been intertwined with for decades. It was a test to confirm whether Ukraine could run on its own power generation without relying on electricity flows from other countries, and a necessary step to complete the country’s longtime goal of integrating with the larger grid that powers most of Europe.

The test, which began on Feb. 24, was supposed to last three days before Ukraine reconnected with Russia. But after only a few hours, Russian forces breached Ukraine’s borders, and a war began, leaving Ukraine’s power grid essentially stranded.

A mad scramble ensued to ensure the country would still be able to count on having electricity during a war. While it wasn’t supposed to synchronize with Europe until next year, Ukraine, along with neighboring Moldova, requested that Europe’s main electricity operator, the European Network of Transmission System Operators for Electricity, expedite matters.

“Ukrainian and Moldovan operators sent letters to the ENTSO-E asking for emergency synchronization at the end of February, which was finally approved by the European operators two weeks later,” Davor Bajs, electricity infrastructure expert at the EU-affiliated Energy Community Secretariat, tells Fortune.

In those two weeks, Ukrainian operators were able to keep energy systems online despite attacks that often specifically targeted energy infrastructure. The 72-hour test was extended well into March as officials lobbied for immediate entry to Europe’s grid.

The European and Ukrainian electricity grids were successfully synched on March 16, accomplishing “a year’s work in two weeks,” the EU’s Commissioner for Energy, Kadri Simson, said in a statement.

Ukraine’s electrical grid was able to weather the storm of the initial invasion and maintain power while becoming synched with Europe’s grid in record time. But this remains an “emergency synchronization, not a normal one,” Bajs says, as several regulatory and legal issues still remain before it can be considered fully integrated with Europe. And as long as the war continues to rage, Ukraine's energy security will be at risk.

‘Never been done before’

It may have been done in two weeks, but synchronizing Ukraine’s electrical grid with Europe’s has been a mammoth task years in the making.

The idea was first explored in 2017, when Ukrenergo, Ukraine’s main energy utility company, struck a deal with ENTSO-E to undergo the lengthy operational and regulatory processes necessary to integrate Ukraine’s grid with Europe’s.

The project was slated to cost over €50 million, and its completion date was initially set for 2026. That timeline was later adjusted to early 2023.

A synchronous electrical grid refers to a network of interconnected power generation and transmission infrastructure that supplies every person, building, and appliance within a grid’s range with a stable supply of electricity. Grids can sometimes become overloaded, often when electricity supply exceeds demand, but in an interconnected grid, power can be transmitted from a region with a surplus of electricity, to one that doesn’t have enough to meet demand.

But not all grids operate the same way. To join a new grid, energy infrastructure needs to become synchronized with its electrical frequencies which can involve using new equipment and instruments. This is exactly what Ukrainian and Moldovan utilities were able to accomplish in record time.

“It is impressive because typically those things take 10 years or more,” Georg Zachmann, an energy and climate policy researcher at the Brussels-based economic think tank Bruegel, told Fortune. “Doing it at that speed has never been done before.”

Zachmann says that a big advantage for Ukraine and Moldova was that over the last few years, their utilities had already laid most of the groundwork to connect their grids with Europe. There was also no need to build any new transmission lines or other major infrastructural projects to complete the switch.

“The grid was there, the preparations were there, and it allowed political bureaus to do it on very short notice,” Zachmann said.

The test at the end of February was one of the last steps in the process before the connection with Europe could be completed. But while synchronizing an energy grid is a complicated engineering task, experts tell Fortune that in Ukraine’s case it was also highly symbolic.

A political switch

Ukraine has been part of Russia’s energy grid since the country’s formation in 1991, and experts say that the move to integrate its energy grid with Europe’s is an indicator of its desire to put some distance between itself and Russia.

“[Synchronization] was clearly also a political symbol,” David Saha, who heads the Low Carbon Ukraine project at Berlin Economics, a German consultancy in energy and economic policy, told Fortune. “It is mainly a technical and symbolic act for Ukraine to be connected and enjoy a secure common energy supply with Europe, and no longer with Russia.”

For years, Ukraine has sought to position itself more as a European state, and less as an ex-Soviet territory. “We need to get back to Central Europe,” Ukrainian Foreign Minister Dmytro Kuleba said in a speech last year. “Central Europe is where our identity belongs.”

This rhetoric of Ukraine becoming closer to Europe and the West angered Putin, who has always seen Ukraine and Ukrainians as an indistinguishable part of Russia. When Ukraine began moving to join Western alliances such as the NATO military accord, Putin reportedly took it as a direct threat to his country’s national security.

Even before the war, extricating itself from Russia was complicated, and energy is the perfect example. Imports accounted for 35% of Ukraine’s energy demand in 2021, according to the U.S. Energy Information Administration, with most of that coming from Russia.

Experts say that what was once a more ideological difference about joining Europe’s energy grid is now a matter of life and death.

Being part of Russia’s power grid meant that Ukraine was severely restricted in trading electricity with Europe, according to Shah. Now that the country is at war, however, having full control over energy supply and stability is critical.

But while Ukraine has taken an important initial step towards decoupling from Russia’s energy clutches, issues still remain before its electrical grid can become fully integrated with Europe’s, and the war only complicates matters.

Waiting for peacetime

Even though Europe and Ukraine are now connected through their power grids, full integration will require more work, and not all of it can be done while the war is ongoing.

Certain technical issues still have to be resolved. For example, some equipment in power plants needs to be re-tuned to fit with European specifications using new devices called power system stabilizers, according to Bajs, while Zachmann pointed out that Ukraine might need a “substantial domestic energy market reform” if it wants to regularly trade electricity with Europe, including abolishing its system of price caps for electricity and potentially even adopting an emissions pricing mechanism to comply with European power regulations.

But experts agree that these problems will have to wait, because as long as the war rages, there is little to be gained from trying to fix them.

“For now we are in an ‘emergency mode,’” Zachmann said. “Especially the legal challenges of setting up an efficient joint market [with Europe], will likely have to wait for calmer times.”

The Russian army has made a practice of attacking and occupying electrical plants in Ukraine, most notably at nuclear power stations Chernobyl and Zaporizhzhia, hurting Ukraine’s ability to keep a stable supply of electricity running through the grid. These incursions have included frequent shelling and missile attacks in the vicinity of crucial energy infrastructure, and regardless of Ukraine’s new link to Europe, damages to these critical components of the grid could change everything. There is also the risk of Russia employing cyber warfare to attack Ukraine’s energy infrastructure, after a number of small hacks in the buildup to the war.

“Synchronization helps,” Zachmann said. “But it does not imply that the system cannot be brought down.”

But despite the problems, the Ukrainian electrical infrastructure has proven to be surprisingly resilient since the war began. A notable drop in electricity demand followed the invasion, as industry came to a near-standstill and millions of refugees left the country. The fluctuating demand might have led to an overloaded grid and even more problems, but operators have so far been able to adjust energy supply accordingly.

“It's not quite so simple to have a system that is really designed for quite a substantial baseload to start working with a very low load, but nevertheless they did manage,” Shah said. “Ukraine has done a very terrific job of keeping the system stable.”

This story was originally featured on Fortune.com