Editing Setthathirath (section)

==Covert plans==
{{See also|Burmese–Siamese War (1568–70)}}
In 1567, King Mahinthrathirat approached King Setthathirath with covert plans for Ayutthaya to rebel against Burma by launching a counterattack against Mahathammarachathirat in Phitsanulok. The plan would involve an overland invasion from Lan Xang with assistance from the royal navy in Ayutthaya passing up the [[Nan River]]. Mahathammarachathirat was in Burma at the time, and Maha Chakkraphat had been allowed to return to Ayutthaya as Burma was facing small rebellions in the [[Shan people|Shan]] areas.{{sfnp|Simms| 1999|p=78–79}}

The plan was discovered and reinforcements were sent to Phitsanulok. Realizing Phitsanulok was too fortified, Setthathirath withdrew his attack, but set up a devastating counter ambush on his retreat to Vientiane in which five pursuing Burmese generals were killed. Seizing on the weakness, King Chakkraphat ordered a second attack on Phitsanulok in which he successfully took the city, but could only briefly hold it having suffered repeated heavy losses.{{sfnp|Simms| 1999|p=78–79}}

King Bayinnaung sent a massive invasion in 1568 in response to the uprising. In early 1569, the city of Ayutthaya was directly under threat and Vientiane sent reinforcements. The Burmese had planned on the reinforcements however and Setthathirath fell into a trap.{{sfnp|Wyatt| 2003|p=82}} After a two-day struggle the Lan Xang forces prevailed at the Pa Sak Valley near [[Phetchabun Province|Phetchabun]], at which point one of the commanding generals from [[Nakhon Phanom]] broke south toward Ayutthaya. The Burmese rallied and were able to destroy the divided forces, and Setthathirath had to retreat toward Viangchan.{{sfnp|Simms| 1999|p=79–81}}

The Burmese then focused their attack on Ayutthaya and took the city. King Setthathirath upon reaching Vientiane ordered an immediate evacuation. The Burmese took several weeks to regroup and rest having taken Ayutthaya, which allowed Setthathirath to rally his forces and plan for prolonged guerrilla warfare. The Burmese arrived in Viangchan and were able to take the lightly defended city. Just as in 1565, Setthathirath began a guerrilla campaign from his base near the [[Nam Ngum River]], northeast of Vientiane. In 1570 Bayinnaung retreated, Setthathirath counterattacked and more than 30,000 were taken prisoner, along with 100 elephants, and 2,300 pieces of ivory from the retreating Burmese.{{sfnp|Simms| 1999|p=79–81}}

In 1571, the Ayutthaya Kingdom and Lan Na were Burmese vassals. Having twice defended Lan Xang from Burmese invasions, King Setthathirath moved south to conduct a campaign against the [[Khmer Empire]]. Defeating the Khmer would have greatly strengthened Lan Xang, giving it vital sea access, trade opportunities, and most importantly, European firearms which had been growing use since the early 1500s. The ''Khmer Chronicles'' record that armies from Lan Xang invaded in 1571 and 1572, during the second invasion King Barom Reacha I was slain in an [[elephant duel]]. The Khmer must have rallied and Lan Xang retreated.