After innocent-looking cargo shipments began catching fire at airports and warehouses in Germany, Britain and Poland over the summer, there was little doubt in Washington and Europe that Russia was behind the sabotage.

But in August, White House officials became increasingly alarmed by secretly obtained intelligence suggesting Moscow had a far larger plan in mind: bringing the war in Ukraine to American shores.

The question was how to send a warning to the one man who could stop it: President Vladimir V. Putin of Russia.

In a series of Situation Room briefings, President Biden’s top aides reviewed details of conversations among top officials of the G.R.U., Russia’s military intelligence arm, who were describing shipments of consumer products that burst into flames — in one case, a small electronic massager — as a test run.

Once the Russians understood how the packages made it past air-cargo screening systems, and how long they took to ship, the next step appeared to be sending them on planes bound for the United States and Canada, where they would trigger fires once they were unloaded.

While the main concern was cargo planes, sometimes passenger planes take smaller packages in spare space in their cargo holds.