The scariest thing about the murder of Boris Nemtsov is that he himself did not scare anyone. “He was no threat to the current Russian leadership and to Vladimir Putin,” said the Russian president’s press secretary, Dmitri Peskov, eerily echoing comments the president made in 2006, when the opposition journalist Anna Politkovskaya was killed. By this Mr. Peskov meant that the Kremlin did not kill Mr. Nemtsov, a former first deputy prime minister, who was gunned down in central Moscow on Friday night.

In all likelihood no one in the Kremlin actually ordered the killing — and this is part of the reason Mr. Nemtsov’s murder marks the beginning of yet another new and frightening period in Russian history. The Kremlin has recently created a loose army of avengers who believe they are acting in the country’s best interests, without receiving any explicit instructions. Despite his lack of political clout, Mr. Nemtsov was a logical first target for this menacing force.

Russia is a country at war — it has been waging battle against Ukraine for a year — and like any country at war, it has focused much of its rhetorical effort on the domestic opposition. The word “opposition” itself is misleading: It suggests having access to media and electoral and social mechanisms, when those have ceased to exist in Russia. More accurately, there are a number of individuals in Russia who are capable of gathering small groups of supporters, waging limited local electoral action, transmitting messages through the tiny remnants of independent media and occasionally organizing street protests.

In the small space available to the Russian opposition, Mr. Nemtsov occupied a unique place. He had become active in politics during perestroika, and in 1991, when Mr. Nemtsov was 32, President Boris Yeltsin appointed him governor of the Nizhny Novgorod Oblast, an important industrial region on the Volga River. Nemtsov was one of the youngest people among the political players of the 1990s, and he seemed to embody the new era: He did not come from the Communist Party nomenklatura, he extolled political and economic reform, and his patronymic indicated that he was Jewish — a fact that he, breaking with the custom of the Soviet era, did not try to hide. In 1997, Mr. Yeltsin asked him to come to Moscow to join the cabinet, and there was talk of him succeeding Mr. Yeltsin as president.