Short answers, pulled from the story.
A few hand grenades exploded near the fortified eastern end of the Great Wall while a commander from the Imperial Japanese Army garrison staged an incident by firing shots to create a pretext for action. The Kwantung Army used this explosion as an excuse to demand evacuation of pass defenses from Chinese forces.
The offensive launched across the region on the 23rd of February 1933 after Emperor Hirohito approved the request for strategic operation against Chinese forces. Chaoyang and Kailu fell by February 25, and Chengde was captured by March 4 when Japanese cavalry and the 1st Special Tank Company took the capital of Rehe.
Sword-armed Northwestern Army soldiers repelled many attacks with traditional blades known as dadaos despite being significantly underarmed compared to their Japanese opponents. Many units were predominantly equipped with handguns, hand grenades, and traditional Chinese swords instead of modern rifles or heavy machine guns.
Chinese forces retreated from remaining positions on the Great Wall on May 20 after being beaten back by overwhelming Japanese firepower. The KMT 29th Army evacuated from Xifengkou Pass on April 8 following heavy losses while Japanese troops retook Lengkou Pass on April 11 after dozens of seesaw fights over the defenses.
Chiang Kai-shek began relocating his forces including units under Huang Jie and Xu Tingyao to reinforce defenses against the Japanese invasion in Baoding. These actions arrived too late and reinforcements proved insufficient to stop the Japanese advance due to timing preventing effective deployment.
Chinese and Japanese representatives met at Tangpu in Tianjin on the 22nd of May 1933 to negotiate an end to conflict resulting in the Tanggu Truce. This agreement created a demilitarized zone extending one hundred kilometers south of the Great Wall that prohibited entry by the Chinese army and acknowledged de facto independence of Manchukuo.