After Baha’u’llah died peace didn't increase. Right the opposite. There were ww1 and ww2. And today things aren't looking good either.
The Bible says that the Christ will reign the world and this is how peaceful it will be in that time:
He shall judge between the nations,
and shall decide disputes for many peoples;
and they shall beat their swords into plowshares,
and their spears into pruning hooks;
nation shall not lift up sword against nation,
neither shall they learn war anymore.
(Isa 2:4)
6And the wolf will dwell with the lamb,
And the leopard will lie down with the young goat,
And the calf and the young lion
[a]and the fattened steer
will be together;
And a little boy will lead them.
7Also the cow and the bear will graze,
Their young will lie down together,
And the lion will eat straw like the ox.
8The nursing child will play by the hole of the cobra,
And the weaned child will put his hand on the viper’s den.
9They will not hurt or destroy in all My holy mountain,
For the earth will be full of the knowledge of the LORD
As the waters cover the sea.
(Isa 11)