U.S. President Barack Obama has vowed to avenge the murder of J. Christopher Stevens, America’s former ambassador to Libya. How he proposes to do this is unclear – historical precedent is of little use.

 

In 1864, the Emperor of Abyssinia took hostage the British consul with some missionaries in the country’s then-capital, Magdala. Three years later, with Emperor Tewodros still refusing to release them, the British dispatched an expeditionary force of 13,000 troops, 26,000 camp followers and 44 elephants.

 

In his book “The Blue Nile,” Alan Moorehead described the expedition thus: “It proceeds first to last with the decorum and heavy inevitability of a Victorian state banquet, complete with ponderous speeches.” Yet it was a fearsome undertaking. After a three-month journey through the mountains, the British reached Magdala, released the hostages, and burned the capital to the ground. Emperor Tewodros committed suicide, the British withdrew, and their commander, Lt. Gen. Sir Robert Napier, was made Baron Napier of Magdala.

Today’s great powers have relied on similar methods, also heavy with rhetoric, against puny opponents, but with far less convincing results...