The Wall Rose invasion was a crisis that began when the Beast Titan turned the Ragako inhabitants into mindless Titans to wander throughout Wall Rose. Eren Jaeger was nearly captured by the Colossal and Armored Titans, though through the combined efforts of the military he was retrieved and Wall Rose was cleared of all Titans.
Prelude: In the aftermath of the 57th Exterior Scouting Mission, the Scout Regiment was summoned to the capital in order to hand Eren Jaeger over to the Military Police Regiment as per the agreement made during Eren's trial a month prior. However, Commander Erwin Smith devised a secret mission for the Scout Regiment to confront and capture Annie Leonhart, a former cadet of the 104th Cadet Corps suspected of being the Female Titan which sabotaged the 57th Expedition. This operation would commence in Stohess District, Annie's stationing as a recruit in the Military Police and the half-way point between Calaneth District and the capital.
The invasion: For reasons unknown, Wall Rose was infiltrated by a foreign assailant. Sometime after his infiltration, he by some means managed to turn the residents of Ragako Village into Titans. These Titans began to wander Wall Rose under his command as the Beast Titan.
Sighting and evacuation: For reasons unknown, Wall Rose was infiltrated by a foreign assailant. Sometime after his infiltration, he by some means managed to turn the residents of Ragako Village into Titans. These Titans began to wander Wall Rose under his command as the Beast Titan.
Utgard Castle: Upon arriving at Utgard Castle over eleven hours after the sighting, the south and west teams discovered that the castle had been inhabited by an unknown individual or group. Various supplies had been left in the castle, with labels marked in an unknown writing. The recruits discussed the events of that day, and Conny mentioned the Titan that was found in his house, noting how it resembled his mother.
Source: Wall Rose invasion (Anime), available under CC BY-SA 3.0.