A table tennis coach, a chaplain’s wife, a dentist and a firebrand nationalist have little in common except a desire to defend their hometown.

And their halting effort to speak Ukrainian instead of Russian, the language that had dominated till recently.

They are among the Ukrainians in Kharkiv who are training for a war with Russia.

If Russia invades, some of the million-plus people here are ready to abandon civilian life and wage an armed campaign against one of the world’s greatest military powers. And they expect many Ukrainians will do the same.

The situation in Kharkiv, just 40km (25 miles) from some of the tens of thousands of Russian troops massed at their border, feels particularly perilous. Ukraine’s second-largest city is one of its industrial centres and includes two factories that restore old Soviet-era tanks or build new ones.

It is also a city of fractures between Ukrainian speakers and those who stick with Russian, between those who enthusiastically volunteer to resist a Russian offensive and those who just want to live their lives.

Which side wins out in Kharkiv could well determine the fate of Ukraine.

The conflict that began in Ukraine’s Donbas region has subsided into low-level trench warfare after agreements brokered by France and Germany. Most of the estimated 14,000 dead were killed in 2014 and 2015, but every month brings new casualties.

An armed resistance by regular citizens defending a hometown of a thousand basement shelters would be a nightmare for Russian military planners, according to analysts and US intelligence officials.

“The Russians want to destroy Ukraine’s combat forces. They don’t want to be in a position where they have to occupy ground, where they have to deal with civilians, where they have to deal with an insurgency,” said James Sherr, an analyst of Russian military strategy who testified last week before a British parliamentary committee.

Russia denies having plans for an offensive but it has demanded guarantees from NATO to keep Ukraine out of the alliance, halt the deployment of NATO weapons near Russian borders and roll back NATO forces from Eastern Europe. NATO and the US call those demands impossible.

Ukrainian President Volodymyr Zelenskyy said recently that any escalation could hinge on Kharkiv. The city is also the base for Yevheniy Murayev, identified by British intelligence as the person Russia was considering installing as president.

“Kharkiv has over 1 million citizens,” Zelenskyy recently told The Washington Post. “It’s not going to be just an occupation; it’s going to be the beginning of a large-scale war.”