Western allies were too slow to supply Ukraine with weapons for its counteroffensive, a think tank says.

Jack Watling, a senior expert on land warfare who wrote the analysis, said the war in Ukraine has “highlighted significant deficiencies” in how Western governments respond to rising threats. “The most glaring deficiency is the inability of Ukraine’s partners to appreciate the lead times between decisions and their desired effects,” Mr. Watling wrote. “This deficiency is being demonstrated at great cost in Ukraine’s current offensive.”