Basho walks across the plain where a great battle once raged. Only empty fields remain. The landscape reminds him of a poem by Tu Fu (712-720), in which the T'ang poet surveyed a similar scene and wrote: 

The whole country devastated,
only mountains and rivers remain.
In springtime, at the ruined castle,
the grass is always green. 

For Basho, the grass blowing in the breeze seems especially poignant, so much so that his eyes well into tears. If Tu Fu, both as a poet and as a man, is a fit model -– to be emulated rather than copied –- Basho is reminded of how little we have learned from all our interminable warfare and bloodshed. The wind blows. The grasses bend. Basho moistens his brush months later and writes, remembering, 

Summer grasses –
after great soldiers’
imperial dreams.
- Basho

 - Sam Hamill, Basho’s Ghost

. . . . .

The blood of great soldiers, courageous young men all
Shed centuries ago, now forgotten
All that's left is the green grass where they fell
Around the ruined castle.

We are on this old rock together,
revolving around the sun,
hurdling through space. 
A marvelous rock, full of diversity, and cycles and mystery. 
We visit here but for a short time. 
Acts of kindness, enjoyment of our time here, adventure
These things actually matter. 

In the end, and there very likely will be an end, perhaps ignominious
Perhaps brought about by the abuse we keep heaping on this beautiful place
Our striving, our power-seeking, all our pride in our possessions and fear of losing them won't matter (we were just passing through). 

The suffering we inflicted on each other over centuries of wars.  Wars over the differences between us -- religious differences, ethnicity, principles and ideals and ideas.

They seemed important at the time.  

The further back in history, the clearer those wars are now
Fought over illusions.
And when we disappear and our hydroelectric dams turn to silt,
And skyscrapers to dust,
All that will have mattered will be the time some of us spent loving this magnificent place. 

Loving each other.  Loving life.