The debris of the Russian plane that crashed in the Sinai. Photo: Twitter.

Evidence that terrorists destroyed a Russian civilian passenger plane over Egypt’s Sinai Peninsula continues to mount, although competent authorities still decline to say so definitively. It speaks volumes, however, that President Obama and British Prime Minister Cameron have already publicly mentioned the possibility of terrorist responsibility. Continued intelligence leaks about a bomb causing the crash and widespread suspensions of commercial flights to Sharm el-Sheikh, where the doomed plane originated, are also telling.

Accordingly, it is hardly premature to assess the consequences if investigators do decide that terrorists deliberately murdered 224 innocent civilians. Sadly reminiscent of Libya’s bombing of Pan Am 103 and UTA 772 under Moammar Qaddafi, the destruction of Metrojet Flight 9268 would prove tragically that the global terrorist threat continues to metastasize.

An ISIS affiliate in Egypt immediately claimed responsibility, but we cannot yet dismiss the Muslim Brotherhood, still locked in its decades-long conflict with Egypt’s military, as the culprit. In either case, terrorism would gravely weaken Egypt’s economy, particularly tourism, which has been struggling to emerge from the Arab Spring’s turmoil and violence. This potentially long-lasting economic damage explains Cairo’s reluctance to conclude publicly that terrorists caused the airliner’s destruction.

Metrojet’s Russian owner, by contrast, was quick to rule out mechanical failure or pilot error for the opposite but equally obvious desire, to escape responsibility. Moscow’s aviation authorities have been more circumspect, perhaps at the Kremlin’s behest.

Vladimir Putin’s bigger problem is the setback the tragedy may pose to his pursuit of a very forward Russian foreign policy, not only in the Middle East, but also in and around the former Soviet Union and even globally. In Ukraine, for example, Putin has reaped nationalist plaudits and political support in substantial part because casualties to the intervening Russian military forces have been so light. Were Moscow’s casualties to increase measurably, which could occur if NATO members were to provide Kiev with adequate weapons, training and advice, the Kremlin’s calculus would change overnight.

Putin’s considerations in the Middle East are similar, but even more problematic from the perspective of Russian domestic politics. His widespread efforts to restore Moscow’s regional influence to Cold War levels currently enjoy general popular approval. If, however, these tragic civilian deaths are in retaliation for Kremlin support to the Assad regime, as the ISIS affiliate has claimed, they directly threaten Putin’s broader strategy.

And if ISIS is responsible, it will be the biggest single mistake these terrorists have ever made. Once the crash’s cause is determined, Putin will have little choice but to inflict punishing retribution, both because he will likely believe it required geopolitically, and for his own domestic political reasons. Otherwise, the murdered civilians, and the risk of even greater anti-Russian terrorism, would call Putin’s penchant for adventurism into question, not just in the Middle East, but also in Europe.

Americans will shed no tears watching Russia destroy ISIS targets. For now, we cannot know whether Russian retribution against ISIS would be a one-time affair or would lead to protracted military conflict. Putin might satisfy his domestic political imperatives with one strike. Whatever the length and extent of the Kremlin’s response, greater Russian military conflict with ISIS does not mean Moscow will solve that problem for us. Moreover, if Putin responds with punishing force against ISIS, America’s regional allies will wonder why Obama has failed to do the same.

Nor will Russian military action alleviate in any way Washington’s fundamental problems in the Middle East. These remain our declining interest and influence; the growth of regional powers like Iran and ISIS that directly threaten America and its allies; and the rise of Russian influence in what was heretofore a U.S.-dominated region. If anything, Washington’s tasks are likely to be complicated by more evidence of vigorous, indeed belligerent Russian activism. And the principal regional threat will still be the terrorist-financing, nuclear-weapons aspirant Iran, which remains Putin’s most important Middle East ally.

Obama’s conduct notwithstanding, there will be no pirouette away from the Middle East for the next president. The global war on terrorism must continue, most definitely including ISIS.

John Bolton, former U.S. ambassador to the United Nations, is a senior fellow at the American Enterprise Institute.

This article was originally published by The Boston Herald.