Solano López accurately assesses the September 1864…

Solano López accurately assesses the September 1864 Brazilian intervention in Uruguay as a slight to the region's lesser powers.

He is also correct in his assumption that neither Brazil nor Argentina pay much attention to Paraguay's interests when they formulate their policies, but he concludes incorrectly that preserving Uruguayan "independence" is crucial to Paraguay's future as a nation.

Consistent with his plans to start a Paraguayan "third force" between Argentina and Brazil, Solano López commits the nation to Uruguay's aid.

When Argentina fails to react to Brazil's invasion of Uruguay, Solano López seizes a Brazilian warship in November 1864.

He quickly follows this move with an invasion of Mato Grosso, Brazil, in March 1865, an action that proves to be one of Paraguay's few successes during the war.

Solano López now decides to strike at his enemy's main force in Uruguay, but Solano Lopéz is unaware that Argentina has acquiesced to Brazil's Uruguay policy and will not support Paraguay against Brazil.

When Solano López requests permission for his army to cross Argentine territory to attack the Brazilian province of Rio Grande do Sul, Argentina refuses.

Undeterred, Solano López sends his forces into Argentina, probably expecting local strongmen to rebel and remove Argentina from the picture.

Instead, the action sets the stage for the May 1865 signing by Argentina, Brazil, and Uruguay (now reduced to puppet status) of the Treaty of the Triple Alliance.

Under the treaty, these nations vow to destroy Solano López's government.