Short answers, pulled from the story.
The 6th and 12th Soviet armies were encircled by German forces near Uman between the 31st of July and the 7th of August. Most units surrendered or were captured after failed breakout attempts, leaving only small parties without heavy weapons to escape.
Colonel General Mikhail Kirponos commanded the Southwestern Front while Marshal Semyon Budyonny led the overall Southwestern Direction. Lieutenant General I. N. Muzychenko led the 6th Army and Major General P. G. Ponedelin commanded the 12th Army within this front.
German units closed the ring of encirclement on the 2nd of August when the 1st Mountain Division reached the Sinyuha River. The 9th Panzer Division joined the 1st Mountain Division, and the 16th Panzer Division met Hungarian Mobile Corps in Pervomaysk to complete the trap.
Four corps commanders and 11 division commanders were taken prisoner along with the two army commanders by the 5th of August. These leaders surrendered after Soviet troops surrounded in forests near villages including Green Brama forest began surrendering on the afternoon of the 7th of August.
The territory held by surrounded Soviet troops measured roughly 10x10 km by the 5th of August. This area sat under total fire from German artillery while fuel ran out for the combined combat order of both armies.