Short answers, pulled from the story.
The battle began on the 1st of September 1939 when the battleship Schleswig-Holstein fired a broadside at the Polish garrison. Captain Gustav Kleikamp gave the order to fire between 04:45 and 04:47 that morning.
Major Henryk Sucharski was the commanding officer but suffered shell shock early in the conflict. Captain Franciszek Dąbrowski effectively took command following Sucharski's breakdown on the second day of the siege.
The defence lasted for seven days starting from the 1st of September 1939 until the 7th of September. The Polish Military Transit Depot originally operated with 88 all ranks stationed there before reinforcements increased the number to about 200 men.
A two-wave air raid by 60 Junkers Ju 87 Stuka dive bombers dropped bombs between 18:05 and 18:25 on the 2nd of September 1939. This attack eliminated the Polish mortars, destroyed their only radio, and shrouded the peninsula in smoke while damaging much of their food supply.
The battle tied up substantial German forces for much longer than expected despite having mostly political importance for both sides. Polish Radio broadcast the phrase Westerplatte fights on repeatedly beginning on the 1st of September 1939 to inspire the nation.