Beware the Ides of March...

On March 15, 1917, Czar Nicholas II was forced to abdicate his throne, ending the Romanov dynasty.

On March 15, 1939, the Nazi's invaded Czechoslovakia...the first non-German speaking country to be invaded.

Most famous of all...
In 44 BC Julius Caesar was killed...even though he had been warned:

According to Suetonius and Plutarch, sometime in March when Caesar was making sacrifices, a soothsayer or astrologer named Spurinna warned Caesar of danger on a date no later than the Ides of March.

According to Plutarch's account, written in 75AD, Caesar had decided, wisely, to remain within the safety of his chambers on 15 March. However, Caesar's 'friend' Decimus (Albinus) Brutus (not Marcus Brutus) managed to convince him that the astrologer's warnings were nothing more than superstition; so Caesar attended the Senate anyway on that date. On his way to the Senate, Caesar contrived to meet up with Spurinna and, upon seeing him mocked, 'The Ides of March are come'. Spurinna replied, 'Yes, they are come, but they are not past'. Later that day Caesar's enemies assassinated him in the Pompeii theatre, at the foot of Pompey's statue, where the Roman Senate was meeting that day in the Temple of Venus.

The noble Brutus
Hath told you Caesar was ambitious.
If it were so, it was a grievous fault,
And grievously hath Caesar answered it....
Come I to speak in Caesar's funeral.
He was my friend, faithful and just to me.
But Brutus says he was ambitious,
And Brutus is an honorable man.
He hath brought many captives home to Rome,
Whose ransoms did the general coffers fill.
Did this in Caesar seem ambitious?
When that the poor have cried, Caesar has wept.
Ambition should be made of sterner stuff.
Yet Brutus says he was ambitious,
And Brutus is an honorable man.
You all did see that on the Lupercal
I thrice presented him a kingly crown,
Which he did thrice refuse.
Was this ambition?
Yet Brutus says he was ambitious,
And sure he is an honorable man.
I speak not to disprove what Brutus spoke,
But here I am to speak what I do know.
You all did love him once, not without cause.
What cause withholds you then to mourn for him?
Speech by Mark Anthony at the funeral of Julius Caesar
From the play "Julius Caesar" by William Shakespeare
Act III Scene 2