Three well-armed militias launched a surprise joint offensive in northeastern Myanmar a year ago, breaking a strategic stalemate with the regime’s military with rapid gains of huge swaths of territory that inspired others to attack around the country. Before the offensive, the military’s control had seemed firmly ensconced with its vast superiority in troops and firepower, and aided with material support from Russia and China. But today it is increasingly on the back foot, with the loss of dozens of outposts, bases and strategic cities that even its leaders concede will be challenging to take back.