Russia’s halting progress in its invasion of Ukraine has puzzled Western observers and analysts, but a senior Pentagon official told The New York Times on Tuesday that Russia’s forces, plagued by low morale and food and fuel shortages, have suffered mass surrenders and self-sabotage by conscripts who “deliberately punched holes in their vehicles’ gas tanks, presumably to avoid combat.” 

The Economist‘s Shashank Josh said a Pentagon source told him “with certainty” that Russians are sabotaging their own military vehicles.

U.S. and European officials said this mix of logistical failures and internal vandalism might explain why a 40-mile convoy of Russian military vehicles from Belarus has slowed to a crawl some 20 miles north of Kyiv, making it a target for Ukraine’s armed forces, the Times reports. Other officials explain Russia’s slow process by pointing to to stiffer-than-expected resistance from the Ukrainian forces and their surprisingly effective air defense, or suggest Russian commanders are just regrouping and calibrating their strategy. 

But Ukraine is celebrating what wins it can over the much larger and more powerful Russian invaders, tactically or in terms of public relations. Ukraine’s National Agency for the Protection Against Corruption (NAPC) tax agency, for example, said in a press release Tuesday that Ukrainians don’t have to declare Russian tanks and other equipment they capture from the enemy, according to Ukraine’s Interfax news service.