When the Romanians joined the war on the side of the Allies, they expected a quick romp to victory and the establishment of a Greater Romania. They banked on Austria-Hungary being on its last legs, thanks to the success of the Brusilov Offensive in Galicia. And the Romanian army has made made good progress in its invasion of Transylvania.
Unfortunately the Romanians seem not to have considered the reactions of Austria-Hungary’s allies. German reinforcements are now heading to Transylvania, preparing to strike back against the invasion. To the south, the Bulgarians have crossed the border and laid siege to the fortress of Turtucaia (known to the Bulgarians as Tutrakan).
After a relief attempt fails, the Turtucaia commander decides that the situation is hopeless. He orders his men to attempt an escape from the Bulgarians by any means they can, and then flees across the Danube by boat, abandoning them to their fate. The Bulgarians storm Turtucaia and Romanian resistance collapses. Some 28,000 prisoners are taken, together with the fort’s store of guns and ammunition.
The defeat leaves the Romanian high command shaken. Perhaps the Bulgarians will exploit their success by crossing the Danube and invading the Romanian heartland. They decline to halt the Transylvanian offensive, for now at least, but they press it less vigorously, fearing that they will have to pull men from there to meet the next Bulgarian move.
Bulgarian attack of the Tutrakan fortress (Wikipedia; painting by Dimitar Giudzhenov)