South Korean activists have angered Pyongyang by firing leaflets across the border at night. Pictured: A barbed-wire fence separating North and South Korea, at Paju, South Korea. Getty Images/Chung Sung-jun

A North Korean soldier who defected to South Korea Wednesday became the fourth soldier to cross the border this year. The soldier came across the de-militarized zone (DMZ), the heavily fortified border that separates the two Koreas created after the Korean War. This year has seen the most military defections since 2000.

An estimated 30,000 people in total, military and civilian, have defected from North Korea since the Korean War. People mostly leave the country through China. A famine in the 1990s helped accelerate defections for a period, but the country years cracked down on people leaving. In addition to soldiers defecting, a number of suspected North Korean sailors, both dead and alive, have washed ashore in Japan this year. The spike in military defections may point to a tougher than usual period inside North Korea, soldiers typically get preferential food rations in the impoverished nation.

The United Nations imposed harsh economic sanctions on the country for its nuclear and missile programs, and North Korean citizens may be bearing the brunt of the punishment.

Dec. 20

A young low-ranking soldier defected to South Korea across the DMZ Thursday, local time, (Wednesday night in the U.S.). The solider is reportedly 19.

“The army has safely secured the defector, and the relevant authorities will investigate the reasons and procedures for the defection,” said South Korea’s Joint Chiefs of Staff spokesman Roh Jae-cheon in a statement to Voice of America.

The soldier appeared through the fog at a checkpoint at a remote point along the border. South Korean soldiers fired several warning shots at a group of North Korean soldiers approaching the border, thought to be looking for their comrade. Soldiers reported the sound of gunfire from the North Korean side later, but it wasn’t clear if it was retaliatory.

Nov. 13

Oh Chong Song, 24, drove to the border in a stolen jeep and was shot several times in a high-profile defection in November. Oh came across near the Joint Security Area on the DMZ — an area where diplomats from both countries can meet for discussions. Oh’s body was discovered in a pile of leaves and retrieved by South Korean soldiers. Oh underwent intensive surgery after massive blood loss and bullets tore through the soldier’s digestive tracks.

Oh was full a number of parasites and had other maladies which pointed to the dismal health conditions in North Korea. Oh was also the son of a ranking military official.

June 18

A soldier in his early 20’s swam across the Han River to defect in June. He was the second solder to defect in a week. The soldier attached foam to himself to float.

“Don’t kill me. I am here to defect,” the North Korean yelled to a South Korean marine who spotted him.

June 12

A teenage soldier approached a guard post northeastern Hwacheon along the DMZ to defect. Crossing the DMZ in more remote areas is difficult — the border is lined with guards, mines and barbed wire.

South Korean soldiers stand guard at the border village of Panmunjom between South and North Korea at the Demilitarized Zone (DMZ) on February 27, 2013 in South Korea. Chung Sung-Jun/GETTY