Alan Hall remembers the first time he met the Christians of Kyiv, Ukraine.

"I worked with the Baptist Church in Ukraine. We worked to get them the materials they needed to help them with their Christian witness."

This was risky work back then, in the 1980s, when Alan was president for international development at the Christian charity Open Doors. It was a time when Ukraine was subsumed into the sprawling communist Soviet Union.

For over 60 years, Open Doors has been providing support for Christians around the world facing persecution for their faith, and life for practising Christians in Ukraine was tough.

Any form of Christian witness was strictly forbidden under the rule of the atheist Soviet Union. However, as Alan remembers, this didn't dampen the spirit of Christians.

"Often in the UK, we can be very passive and reactive about our faith," he says. "The church in places like Kyiv wasn't reactionary, Christians were living their faith, they were working it out proactively."

The most sought-after resource in all the nations of the Soviet empire were Bibles, and Open Doors, in the footsteps of its founder, Brother Andrew had been smuggling them into Ukraine by the thousands.

There has been no need to do that for Ukrainian Christians for over three decades now. Ukraine left the USSR in 1990. And whereas some post-Soviet nations have slidden into totalitarianism, religious freedom has remained untouched there. Most of the country still identifies as Christian, and nearly two thirds belong to branches of the Orthodox Church.

In the last few days, as Russian tanks advance on the major cities, citizens have taken to the streets to fight, afraid they might lose vital freedoms such as democracy. What about religious freedoms though? Could Ukraine return to the bad old days of underground churches and smuggled Bibles?

Russia itself has tightened up its legislation against some forms of missionary activity, with the controversial Yarovaya law, which was passed in 2016. It sees the government imposing legal restrictions and controls over churches, with church leaders sometimes facing interrogation.

However, according to Rolf Zeegers, who works as a Persecution Analyst for Open Doors, even if the Russian invasion is successful, Ukraine's churches are unlikely to see a return to Soviet days.

"I don't think Russia is seeking to annexe Ukraine, so we don't need to expect the implementation of Russia's anti-missionary legislation in Ukraine. However, there would be restrictions.

"Churches could be prevented from getting funds from abroad, having visiting pastors from abroad, who would otherwise provide training as well as imported Christian literature. Even so, I do not expect a wave of arrests and detentions."

However, he agrees that the two 'rebel' regions, Donetsk and Luhansk, whose new leaders have looked to Moscow for support, have seen the churches stripped of some of their freedoms since 2014.

"It's a different situation in the two rebel regions, where the rebels have been developing their own policies regarding religion. Officials have confiscated Christian literature and churches have been prevented from meeting when the regional authorities have denied them the necessary registration."

One key difference between today and the days of Soviet occupation is that President Vladimir Putin's Russia is no atheist state. Indeed, in order to affirm his nationalism, Putin has been getting closer to the ancient Russian Orthodox Church in recent years. The Church's leaders have often frowned upon the presence of other denominations, including Baptists and even Roman Catholics in a region they have considered rightfully theirs.

There are similar feelings of toes being stepped upon in Ukraine, where the Russian Orthodox Church has been present - as it has in Russia - for over a thousand years. However, it has a rival. The Ukrainian Orthodox Church has been present there for nearly 500 years. And in 2019 it was officially acknowledged by the Ecumenical Patriarchate of Constantinople as a legitimate Orthodox Church in its own right, finally cutting ties with the Moscow Patriarchate.

Relations between the two wings of Orthodox Christianity have not been especially cordial, as Alan remembers from the days of communism.

"I can tell you that in my dealings with the Russian Orthodox Church in those years, there was no love lost between the Russian Orthodox Church and the Ukrainian Orthodox Church," he says. "They were poles apart."

This could spell trouble according to Rolf.

"What may happen if Ukraine steps into the fold of Russia again, is that the Ukrainian Orthodox Church may be under pressure to unite again with Moscow," he says. "And if they don't want that, then we will have problems."

However, he doesn't think the Russian Orthodox Church holds the same sway in Russia now as it did in Tsarist days: "Don't forget that 70 years of atheist Communism blotted out quite a lot of the old influences that the Russian Orthodox Church had on state bodies. And Putin has never recognised them as the official state church."

Ironically, the current planned invasion appears to be bringing both wings of Orthodoxy – and the whole Christian Church in Ukraine - closer together.

"I've seen statements from the Ukrainian and the Russian Orthodox Churches in Ukraine condemning the invasion. I've seen the Greek Orthodox Church and the Roman Catholic Church in Ukraine saying the same thing. The Baptists have been asking for prayer. They are all of one mind on this - none of the Christian communities are backing Moscow."

One thing there is not official agreement on is how Ukraine's Christians should respond to the invasion. As ordinary citizens are picking up guns and Molotov cocktails, what role should they play?

"We urgently need to pray that Ukraine's believers will listen for the voice of the Lord, for guidance and wisdom in this situation - so that they will be able to stand strong and spread the gospel despite, everything that is going on around them."

Alan is convinced that, while the church there may have been free of Soviet persecution since 1990, its passionate commitment to the Gospel has not been erased by relative ease of subsequent decades.

He says: "I think the spirit of people there means that they will still stand by the faith and whether they're old or young the church will stand. The church will grow and the church will continue to live out its Christian convictions.

"I think we should pray that they will be resolute, be wise, be warned and be ready to serve the Lord."

Pray for the churches in Ukraine

• Ask for God to grant them wisdom as they seek to decide if and how to resist the Russian invasion.
• Pray that this troubled time will work to bring a stronger unity between all the Christian denominations.
• Pray for God to strengthen and inspire the churches to serve the communities inspirationally during these troubles.