If we are at war, who is the enemy?

There will be many wrong ways to answer that question in the coming weeks and months.

Last week, President Trump declared himself a “wartime president.” And wartime leaders generally mobilize people not only by rallying them to a common defense but also by uniting them in a shared hostility.

But what happens when the foe is an invisible virus? As hardship intensifies, the desire to demonize will be no less intense than in past wars.

Trump, always a leader in blaming others, has turned almost instinctively to a familiar target, lashing out at the media, which he has branded before as an “enemy.” Because he can never admit fault — in this case, bungling the initial response to the crisis and underestimating the danger — he has to undermine honest reporting as fake news.

That is corrosive at the best of times. In a moment like this, when fear and uncertainty can be countered only by transparency and trust, scapegoating the press will be especially ­destructive.

In pointedly discussing the “China virus,” Trump fingers another possible target, and some conservative politicians are eagerly taking his cue, seeing this as an opportunity to stoke a new Cold War and promote economic ­“decoupling.”

“We will emerge stronger from this challenge, we will hold accountable those who inflicted it on the world, and we will prosper in the new day,” said Sen. Tom Cotton (R-Ark.).

The Chinese Communist Party is undoubtedly odious — responsible for an ongoing crime against humanity in western China, mercilessly repressing its own people, fashioning a surveillance state the likes of which we have never seen. Its suppression of news of the virus in its early stages in Wuhan is unforgivable, and its expulsion of foreign journalists — including from The Post — will deepen suspicion.

But covid-19 is not a biological weapon that China inflicted on the world, and anti-China policies that weren’t in our interest before will be no more rational now in the guise of “holding China accountable.” As before the pandemic, the U.S.-China relationship will be complex, with elements of competition and cooperation. Setting China up as the hostile power in this war won’t help us get that right.

But even that isn’t the biggest danger of this war without enemies. The biggest danger is that we will turn it into a new kind of civil war.

After all, we are being told that we can limit the spread of this disease if we all behave appropriately. So anyone who contracts covid-19, or watches a loved one die after contracting it, will be tempted to blame those who did not behave appropriately — who were “not only dumb but also extremely selfish,” as one doctor said on Twitter after watching partygoers carry on in ­Nashville.

At the same time, many Americans will be harmed, not directly by the virus, but by measures being taken to limit its spread. People are losing jobs, some never to be recovered. Small businesses built up over years or decades are shuttering, some never to reopen. Children will fall behind in school. Stress, loneliness, even hunger will contribute to illness and even some deaths.

Will some people be tempted to blame their woes on the officials who shut down the economy to “flatten the curve”? Or on the elderly and ill, who are most vulnerable to the virus? Of course. It’s only human.

What’s called for to avoid this civil war is something just as human — a touch of empathy and understanding. This shutdown has descended on us with ferocious suddenness; it’s not surprising that some young people are slow to get the message.

And the social distancing, it has to be understood, is not only to protect the elderly and vulnerable, but to keep the health system from being swamped, which would endanger young as well as old. Young who, incidentally, are not immune from covid-19’s dangers, either.

So far, Americans — like Italians and Spaniards, Singaporeans and South Koreans — should feel proud that it is the empathy, not the scapegoating, that has the upper hand. The sacrifices that are being made voluntarily are astounding.

But unless we get really lucky, this is going to feel like a long haul — a long war. And it will be a war with no enemy — not the media, not China, not each other. We are going to have to summon our common purpose without falling back on hate.

Read more: